How did Hitler behave towards all those whom he knew in his childhood and youth after he rose to power?

Besides the physician, I believe Hitler's WW1 commanding officer (for a short time) was a baptized Jew named Hess who received temporary special treatment that may or may not have been the result of direct intercession by Hitler.

A non-Jew, a woman named Stefanie, was someone Hitler had had a crush on in his youth and she was surprised to discover that the Fuhrer had felt this way. He sent her gifts while in power but they never met.

Thomas Weber's book 'Hitler's First War' says the following (in summary, I am not quoting the book directly):

After a short stint in a combat role early in the First Battle of Ypres in late 1914, in the last phase of the mobile war before the trench lines were fully formed, Hitler then spent the rest of the war as a dispatch carrier attached to the headquarters of his regiment (16th Bavarian Reserve Infantry, also called the List Regiment), in at least comparative safety and comfort compared to the front line infantry in the trenches.

Whether he made truly close friends is questionable, but on his way to power and in power Hitler retained links with and did promote some of his fellow dispatch runners and the sergeant who had commanded them from his days with the 16th Bavarian Reserve Infantry 1914-18, some of whom in turn became loyal Nazis.

The fact that Hitler spent most of the war as a regimental dispatch carrier had significant consequences. First, he and most of his colleagues survived the war: he never experienced the attrition or destruction of the group of men he closely served with, as front line soldiers did, sometimes repeatedly. Second, he and his fellow headquarters staff with their cushier billets in villages behind the front line were never much liked by the front line troops. The only time Hitler attended a regimental reunion after the war he found he was not popular and did not attend again.

Hitler was not particularly patronizing, but he definitely supported people he liked from his early life. For example, as a young man he reportedly had an affair with a French girl named Charlotte Lobjoie by whom he had a son, and she told her son that Hitler always sent her money.

Hitler was kind of a loner, so he didn't have many friends when he was young. His best friend, August Kubizek, he fell out of touch with during the War, but in the 1930s they were briefly reacquainted and he offered him a valuable position and money to educate his children. If you are interested in Hitler's personality you might want to read Kubizek's book.

Hitler was way too idealistic to hold petty grudges. He viewed himself as the savior of the German people. His mind was filled with delusions of grandeur, not revenge fantasies.

August Kubizek is another individual with whom Hitler seemed to have sustained some bonds of friendship. I've read about him in Brigitte Hamann's Hitler's Vienna: A Portrait of the Tyrant as a Young Man, which perhaps is a very good overall source on the topic.

It was Adolf Hitler who, at the age of eighteen, successfully persuaded Kubizek's father to let his son go to the metropolis to attend the [Vienna Conservatory]. This, Kubizek wrote, changed the course of his life for good ...

Kubizek saw Hitler for the last time on 23 July 1940, although as late as 1944 Hitler sent Kubizek's mother a food basket for her 80th birthday ...

When the tide began to turn against Hitler's favour, Kubizek, who had avoided politics all his life, became a member of the NSDAP in 1942 as a gesture of loyalty to his friend.

The case of Eduard Bloch is relevant if untypical in humanity considering Hitler's character:

Eduard Bloch (30 January 1872 – 1 June 1945) was a Jewish-Austrian doctor practicing in Linz (Austria). Until 1907 Bloch was the doctor of Adolf Hitler's family. Hitler later gave Bloch special protection after the Nazi annexing of Austria ...

The sixty-six-year-old Bloch wrote a letter to Hitler asking for help and was as a consequence put under special protection by the Gestapo. He was the only Jew in Linz with this status. Bloch stayed in his house with his wife undisturbed until the formalities for his emigration to the United States were completed ...

In 1940 Bloch emigrated and lived in the Bronx ...