I have been to Poland and Auschwitz recently
Auschwitz has no admission fee so you are not supporting them that way, Besides its not free to Maintain, there is alot of security there , metal detectors, guards , tour guides and other maintainance to keep the place safe. Ill assume you are buying Kosher food (Actually quite easily available in Poland, especially in Warsaw and Krakow) . You are buying them from Jews so you really arent supporting the Poles
You are supporting them by staying at a Hotel and flying in, however not all all Poles support this policy especially in Krakow which is the basic center of Jewish life in Poland today
There are very few survivors left, notbody to tell the story, the only witnesses to the attrocities are the camps themselves and I can tell you its not the same as pictures, Nothing can prepare you for a visit to Auschwitz, you just have to go. You will not forget it