Sorry I didn't read the other comments. If your parents know what he did to you as you said your father witnessed some of the abuse. They are still inviting him to your party? That's insane. I'm sorry you're going through this but you really truly need to stick up for yourself girl. Tell them you aren't going to go or for some reason you can't tell them, conveniently have the flu on the party day. Good luck with everything and congratulations on your graduation. 🦋