Steve is defensive especially now that Don has pointed out that nobody knows what he has been doing in the basement. The evidence suggests that Steve is going to get angry at Steve for accusing him of causing all of the strange goings on in the neighborhood. To Don, this anger is more evidence that Steve is up to something.
I believe so because Gatsby was a wealthy man who was poor at first and worked his way to become rich and the woman he loved was also rich and had a high class. The poorer people were lower class in the book/movie as well
