Did American policymakers seriously consider scaling down Lend Lease Aid to the Soviet Union after the battle of Kursk?

Question 1-3: Did American policymakers seriously consider scaling down Lend Lease Aid to the Soviet Union after the battle of Kursk?

Short Answer:
No, while there was always much debate about the scale of US aid to the Soviet Union during WWII, before and after the battle of Kursk the United States was more concerned with the Soviet Union seeking a separate peace with Hitler than with poor behavior by the Soviets after WWII with all that aid. Coincidentally the soviets were also concerned with the Allies, British and the United States would negotiate a separate peace with Hitler throughout the war.

Detailed Answer:

WWII aid to the Soviet Union from the United States refers to 5 periods. Pre Lend-lease and four protocols of Lend-lease.

US deliveries to the Soviet Union

• pre Lend-lease June 22, 1941 to September 30, 1941 (paid for in gold and other minerals)
• first protocol period from October 1, 1941 to June 30, 1942 (signed October 7, 1941),[41] these supplies were to be manufactured and delivered by the UK with US credit financing.
• second protocol period from July 1, 1942 to June 30, 1943 (signed October 6, 1942)
• third protocol period from July 1, 1943 to June 30, 1944 (signed October 19, 1943)
• fourth protocol period from July 1, 1944, (signed April 17, 1945), formally ended May 12, 1945 but deliveries continued for the duration of the war with Japan (which the Soviet Union entered on August 8, 1945) under the "Milepost" agreement until September 2, 1945 when Japan capitulated. On September 20, 1945 all Lend-Lease to the Soviet Union was terminated.

There was always talk by American policymakers in opposition to aid given to the Soviet Union. From the American perspective U.S. Soviet relations had been significantly strained prior to WWII; and the Soviet's non aggression pact with Hitler in 1939, their occupation of eastern Poland, siezures of the Baltic states and their winter war with Finland greatly soured what was a bad acquaintance. When WWII began the United States had imposed a “moral embargo” on the Soviet Union.

Dec 2, 1939
The Roosevelt Administration imposed a "moral embargo" on the Soviet Union and urged American companies not to sell the Soviets airplanes or components in their manufacture.2

United States Congress had significant reservations to granting Lend Lease Aid to the Soviet Union.

FDR approves Lend-Lease aid to the USSR Although the Soviet Union had already been the recipient of American military weapons, and now had been promised $1 billion in financial aid, formal approval to extend the Lend-Lease program to the USSR had to be given by Congress. Anticommunist feeling meant much heated debate, but Congress finally gave its approval to the extension on November 7, 1941.

The aid extended to the Soviet Union wasn't the sort which merely accelerated the Soviet's eventual victory. It was more substantial than that. The aid began early in the Soviet German war, June of 1941 when many believed the Soviet existence was in jeprody.

• Soviet commander admits USSR came close to defeat by Nazis
• The evidence is overwhelming that the Nazi attack came as a total surprise and shock to Stalin. Describing Stalin's reaction to the events of June, Nikita Khrushchev pictured him in collapse, thinking "this was the end".
  "All that Lenin created we have lost forever," Stalin exclaimed. In Khrushchev's words, Stalin "ceased to do anything whatever," did not for a long time direct military operations and finally returned to activity only when the Politburo persuaded him he must because of the national crisis. The 900 Days: The Siege Of Leningrad

The aid was large and got larger and was existentially significant for the Soviet War effort. It began in June of 1941 with 1 Billion Dollars worth of gold bullion to allow the Soviet's to buy supplies. By the end of the war the supplies provided by the United States alone were comparable to the supplies produced by the United States for it's own troops in Europe ( 17.5 million tons for the Soviets vs 22 million tons for U.S. armed forces ) and totaled about 11 Billion dollars worth of supplies. .

Lend Lease: US deliveries to the Soviet Union

• Roughly 17.5 million tons of military equipment, vehicles, industrial supplies, and food were shipped from the Western Hemisphere to the USSR, 94% coming from the US. For comparison, a total of 22 million tons landed in Europe to supply American forces from January 1942 to May 1945.
• It has been estimated that American deliveries to the USSR through the Persian Corridor (1 of four path's for lend lease goods to Soviet Union) alone were sufficient, by US Army standards, to maintain sixty combat divisions in the line.
• The United States delivered to the Soviet Union from October 1, 1941 to May 31, 1945 the following:
  • 427,284 trucks,
  • 13,303 combat vehicles,
  • 35,170 motorcycles,
  • 2,328 ordnance service vehicles,
  • 2,670,371 tons of petroleum products (gasoline and oil) or 57.8 percent of the High-octane aviation fuel,
  • 4,478,116 tons of foodstuffs (canned meats, sugar, flour, salt, etc.),
  • 1,911 steam locomotives,
  • 66 Diesel locomotives,
  • 9,920 flat cars,
  • 1,000 dump cars, 120 tank cars,
  • 35 heavy machinery cars. Provided
  • 53 percent of total domestic production of ordnance goods (ammunition, artillery shells, mines, assorted explosives) .
• One item typical of many was a tire plant that was lifted bodily from the Ford Company's River Rouge Plant and transferred to the USSR. The 1947 money value of the supplies and services amounted to about eleven billion dollars.

So the answer to the Question was yes, there was serious discussions inside the United States about extending and maintaining United States aid to the Soviet Union. However; Kursk was not the when the alliance was particularly strained. The alliance came under the most strain with regard to..

U.S.-Soviet Alliance, 1941–1945

1. The reiniging on opening up a second front in Europe. Roosevelt had promised to open up a second front in Europe by the autumn of 1942 and failed. Failed again in 1943, and only succeeded in May of 1944.
2. August of 1944, When the Soviet's refused to aid the Polish home army with the Warsaw uprising.
3. March of 1945, When Britain and America chose to exclude the Soviets from secret negotiations with German officers over surrender of German troops in Italy. Operation Sunrise

Question 2 of 3:
Meaning that the Americans could have been the first to arrive in Berlin, and perhaps Warsaw or even points further east.

There is no need to have an alternate view of reality for a US invasion of Berlin. The United States could arguable have reached Berlin if it had chosen to. Eisenhower chose not to take Berlin. Berlin was heavily fortified, and it was estimated would cost 100,000 casualties to take the city. Europe had already been split into spheres of interest for each of the Allies at Yalta, and Berlin was in the Soviet sphere.

What if Eisenhower Had Driven On to Berlin?
Taking Berlin might cost up to 100,000 casualties, notes Gen. Omar Bradley: “a pretty stiff price to pay for a prestige objective, especially when we’ll have to fall back and let the other fellow take over.”

That and the fear of an accidental clash between the Soviets, American and British Armies if they came into close proximity were the reasons Eisenhower elected to stop his advance at the Elbe River 50 miles outside of Berlin and leave the city to the Soviets.

As for Points further to the east. US General George Patton had gone into Czechoslovakia in 1945.

Czechs mark anniversary of liberation by American troops in WWII

But by the terms of the Yalta Conference. Czechoslovokia was in the Soviet Zone, so all the territory taken by Patton had to be handed over to the Soviets.

Question 3 of 3:
Did anyone in the U.S. military or government advocate such a "Machiavellian" policy? Were there people who counterargued that keeping up the flow of Lend Lease aid would save American lives?

The allies were more afraid of the Soviet's anger in the summer of 1943 than they were about post WWII bad soviet behavior with all the aid being shipped to them. The dominant fear of the Soviet's anger was tied up with the allies failure to live up to promises given to Joseph Stalin about opening of a Western Front in Europe against Germany in autumn of 1942, (fail), 1943(fail) but only succeeding in May of 1944 D-Day Landing. The fear was the Soviets forging a separate peace with Germany. Which really would have hurt the allies. One can argue that all British and American victories in Europe against the Nazi's were achieved due to Hitler's commitment and overwhelming concentrating his forces against the Soviets. All the allies WWII successes came about with the Soviet War effort drawing the bulk of Hitler's attention. The Soviet's did the overwhelming majority of the fighting and dying in WWII. The pragmatists view of WWII in 1943 was Stalin wasn't happy about the role he was being forced to play (from his perspective), and he would try to reshuffle the deck by seeking an independent peace with Hitler.

Research Starters: Worldwide Deaths in World War II

                          Military                   Total Civilian & Military
        Soviet Union      8,800,000-10,700,000       24,000,000
        Germany.          5,533,000                   6,600,000-8,800,000
        United Kingdom      383,600                     450,700
        United States       416,800                     418,500

(*) Note these are total WWII Deaths. Britain and America fought entire wars in the Pacific in WWII, which the Soviet's did not participate in until the final few days of that conflict. Thus US and Britains actual military deaths with regard to European theatre in the above numbers are somewhat inflated.

http://www.ibiblio.org/hyperwar/USA/BigL/BigL-5.html lists Lend Lease provisions by the US to the USSR only for 1941 through 1943, not for '44 and '45 (if any), as the data was taken from a 1944 congressional report. It does show a steady increase for those 3 consecutive years though, not a decline or flattening out for 1943.
From the total deliveries also mentioned to the USSR, subtracting from those the totals up to 1944, I can however conclude that there was no decline (deliveries in 1944 and 1945 combined totaled more than those from 1941-1943 combined, though the focus seems to have shifted from aircraft and armoured vehicles to trucks and utility vehicles).
The website is specific to the US program of course, and does not mention the British aid to the USSR in the same period.

Short Answer

Neither Roosevelt nor the members of his Soviet Protocol Committee (which effectively determined lend-lease policy for the Soviets) were prepared to consider any reduction in lend-lease shipments to the Soviet Union following the Battle of Kursk, or even in mid 1944.

Roosevelt, through his closest advisor Harry Hopkins, kept close control of lend-lease to the Soviet Union, seeing it as vital in gaining Soviet trust in the long-term. This was despite there being people in both the US government and in the military who argued for a reduction in lend-lease to the Soviets from at least mid 1943.

A memo dated 4 February 1944 from Harry Hopkins, Chairman of the President’s Soviet Protocol Committee, to Averell Harriman, U. S. Ambassador in Moscow, clearly states the administration's policy:

...since no one can now determine when the war will be over, it seems preferable that there should be no interruption in the procurement of supplies for the USSR war program...

The arguments used to justify a reduction were mostly about the misuse of supplies. There was also advice against providing military equipment which strengthened the Red Army and warnings that the Stalin was taking advantage of American generosity. These arguments, though, did not come from those who dictated policy.

Despite these concerns, there was no reduction in supplies until Truman became president.

Details

In Lend-Lease in Early Post-war Soviet-American Relations, K.V.Minkova notes that

even in the early stages of Lend-Lease, some officials from Roosevelt’s team tried to persuade him to limit the U.S. aid to Moscow (at least by those positions that directly strengthened the military power of the U.S.S.R. — e.g. by aircraft) or to provide this assistance on a reciprocal basis — i.e. in exchange for gold, strategic metals, etc. Admiral W. Standley, who preceded W. Averell Harriman as U. S. Ambassador to the U.S.S.R., kept warning Roosevelt that the Soviet leadership was taking advantage of his generosity.

Standley's concerns were dismissed by Hopkins, and those in charge of policy making evidently felt the Admiral was damaging US - Soviet relations, as witnessed by this memo The Executive of the President’s Soviet Protocol Committee [J. D. Burns] to the President’s Special Assistant [Hopkins], dated August 10th 1943:

We now have a number of United States representatives in contact with Russian representatives who do not trust Russia and who do not follow a national policy of the “good neighbor and sincere friend” to Russia. They obviously do not develop mutual trust and friendliness. These should either be replaced or they should be required to pledge loyal support to the above policy.

Unsurprisingly, Standley was recalled from Moscow on Sept. 18th (though this had been on the cards since at least May). Burns also states the importance of the Soviet contribution in tying up German divisions and that she was critical in the effort to defeat Nazi Germany:

In War II Russia occupies a dominant position and is the decisive factor looking toward the defeat of the Axis in Europe. While in Sicily the forces of Great Britain and the United States are being opposed by 2 German divisions, the Russian front is receiving attention of approximately 200 German divisions. Whenever the Allies open a second front on the continent, it will be decidedly a secondary front to that of Russia; theirs will continue to be the main effort. Without Russia in the war, the Axis cannot be defeated in Europe,...

(my emphasis)

Despite this, concerns over the way the Soviets were using the supplies the US was sending through lend-lease were being raised by at least mid 1943. Citing evidence which includes the Minutes of the Executive Staff Committee, Office of Lend-Lease Administration, July 13, 1943, George C. Herring, Jr in Lend-Lease to Russia and the Origins of the Cold War, 1944-1945 in the The Journal of American History (1969) states that the Soviets

...had requested vast quantities of industrial equipment which could not be made operational before the end of the war and which was obviously intended for postwar reconstruction.

Edward R. Stettinius, Jr, then Under Secretary of State, expressed similar concerns in a memo to Dean Acheson dated December 27, 1943. Disquiet over the misuse of supplies was particularly evident in the latter half of 1944. Citing W. Averell Harriman, then US ambassador to the Soviet Union, Herring also notes that later, in 1944, the Soviets

...were giving or selling to other countries American supplies or items similar to those received under lend-lease in order to boost their own political influence in Eastern Europe and the Middle East.

More pointedly, and edging closer to concerns over the Soviet advance into Eastern Europe, Major General John R. Deane, then chief of the United States Military Mission in Moscow, wrote a letter to Roosevelt's chief of staff, George Marshall on 2 December 1944:

'Everyone will agree on the importance of collaboration with Russia - now and in the future [but] it won't be worth a hoot, however, unless it is based on mutual respect and made to work both ways . . . when the Red Army was back on its heels, it was right for us to give them all possible assistance with no question asked ... the situation has changed, but our policy has not.' Clearly irked, Deane went on: 'Some will say that the Red Army has won the war for us. I can swallow all of this but the last two words.'

Source: Diane S. Clemens, Averell Harriman, John Deane, the Joint Chiefs of Staff, and the 'Reversal of Co-operation' with the Soviet Union in April 1945 (The International History Review, May 1992)

Nonetheless, although not unconcerned about these 'abuses' in the way supplies were being used, the policy makers did not reduce aid:

...lend-lease to Russia was given a unique status....As the military position of the Allies improved after mid-1944 and American troops took on a greater burden of the fighting, lend-lease to most nations was sharply reduced.

None of these limitations applied to Russian lend-lease....Difficulties in transporting supplies to Russia imposed severe limitations on the lend-lease program until 1943, but as the shipping crisis eased, protocol commitments steadily increased and were often exceeded.

This is fully consistent with the views expressed by the Soviet Protocol Committee in mid 1943. Not until Truman became president did the policy significantly change.