I stayed with friends while I was still in high school and my mother and other people understood why, that I just needed to be away from the house, not that my mother was really abusing me at the time. I may have thought she was emotionally abusing me, because of my PTSD, but I just needed that resort. Maybe your parents would understand this. Or you could just tell them, "I'm going to stay with a friend for this last month if you let him back in the house, because I have to protect myself and I'm working through things in therapy right now that had to do with him and him being around me would make me fall apart".

I can understand this, when you're doing trauma work, it brings out those emotions that you had during the abuse and being around your attacker will throw you for a loop. You'll start to be REALLY afraid. At least, that is how I've felt. When I remember thing, have flashbacks, or try to work on my books, then my father comes over, oh gosh, it's constant anxiety, fear, anger, rage, depression, etc. You'll probably start feeling all those feelings again and get scared to work on your trauma.

I hope you can either get your parents to wait to let him back in for a month, (I mean, doesn't he have any friends he could stay with???) or stay with a friend or other family member yourself.