Was Alexander Coffroth for or against slavery? And in what instances?

Coffroth was a moderate

When we talk about American society during and immediately before Civil War, we could roughly divide it into three groups. First were abolitionists, centered among Republicans, especially Radical Republicans and they demanded immediate end of institution of slavery in the Union. It must be said that even more moderate Republicans, like Abraham Lincoln, essentially admitted that house divided cannot stand, i.e. that US cannot continue as a Union with some states and territories allowing slavery and some don't . Since it was practically impossible to introduce slavery into more populous Northern States, this essentially argued that slavery must be abolished. Second group were pro-slavery secessionist. They were reverse side of coin to abolitionists, centered mostly among Southern Democrats. They also agreed that US cannot continue as a Union with with such a difference in legal and generally social system, therefore they concluded that Southern States should secede from the Union.

Third group, most interesting to us since Alexander Hamilton Coffroth belonged to it, is often omitted from historical narrative, but was perhaps most numerous in US population and sadly least organized. These were the people who were not so much interested in slavery, wanted to preserve Union, and above other things wanted to prevent war and to stop it as soon as possible when already started. To understand them, it is enough to simply mention that at least 620 000 soldiers died in US civil war (850 000 total according to some newer research) , roughly 4% of US male population. It was most bloody war in US history, especially in the South, with corresponding economic devastation.

Anyway, Coffroth was Northern Democrat from Pennsylvania. He personally didn't own slaves and didn't lobby for allowing slavery in his home state, but did support right of the Southern States to regulate this question according to their own interests and will. As such, on the eve of the war, he supported Crittenden amendments to US constitution, which would permanently divide US to free and slave states and ban Congress from interfering into institution of slavery. When this failed, and war started, his political work mostly revolved around finding compromise with Southerns and those slave states that remained into Union like Kentucky. Coffroth was mostly concerned about the property rights, and demanded that slave holders be compensated for freed slaves (something that British did when they abolished slavery) .Nevertheless, he did vote for Thirteenth Amendment that abolished slavery.

For his views about the race, he certainly did not view Blacks as equal to Whites

It proposes to set free four million of ignorant and debased negroes to swarm the country with pestilential effect. it is to carry out the design of the bad and wicked men, whose fanatical teaching has produced the terrible bloodshed and destruction of life through which we are now passing.

However, this was not something unusual and uncommon in those days. Even Abraham Lincoln, abolitionist himself, agreed that Blacks are not equal to Whites :

I will say then that I am not, nor ever have been, in favor of bringing about in any way the social and political equality of the white and black races, that I am not nor ever have been in favor of making voters or jurors of negroes, nor of qualifying them to hold office, nor to intermarry with white people; and I will say in addition to this that there is a physical difference between the white and black races which I believe will forever forbid the two races living together on terms of social and political equality. And inasmuch as they cannot so live, while they do remain together there must be the position of superior and inferior, and I as much as any other man am in favor of having the superior position assigned to the white race. I say upon this occasion I do not perceive that because the white man is to have the superior position the negro should be denied every thing. I do not understand that because I do not want a negro woman for a slave I must necessarily want her for a wife.

As we can see, idea that all human races are equal was not popular and would be in fact object of ridicule in those days. Even those that wanted to free slaves like Lincoln did not agree that Whites and Blacks are equal. This came much latter, let's say from 1960's . In fact, even after the war most of Americans were quite content that Black slaves were freed, but didn't want them in place of power, despite Fourteenth and Fifteenth amendment that gave full citizen rights to Black freedmen. This later led to Compromise of 1877 and situation in the South that did not much change until Civil Rights movement in already mentioned 1960's.