Wow, you're story is really hot and I'm glad you're enjoying it. I'm also really relieved that he gave you the money back. I was worried about that.
Like some of the others have said, though, be careful. By what you've said, it sounds like you and him are already in a pretty abusive relationship. Hopefully, it's only for the role-playing, but if it extends beyond that, take a stand. Regardless of whether you like to be humiliated during sex, you deserved to be respected by your friend.
Keep us posted on your stories, though! They're really hot! :thumbs up: