You could always send him a bill after you move out for the time to clean the "common" areas of the appartment. Or at least bring that up in conversation. He forgets that you're going to be doing the cleaning once he ditches the place.
Also, You could just call his bluff that he won't make a small claims suit
Lawyers are mostly talk anyway - even this wanna-be one.
Just to be safe make photocopies and pictures of everything!