Answer:
1.) Auschwitz was a nightmare for Jews full of fear, uncertainty, and darkness. Therefore, the author compares the camp to a never-ending night because it was exactly like that. In the night, there is danger and criminals don't have to worry about being seen due to a lack of light.
2.) The author refers to Hitler and the other leaders of the camp as possessing a "demented mind" because the things that occurred in the camp were nothing short of devilish and cruel. I think the author believes that these leaders might even be a bit crazy or mentally unstable to create such a place.