He's talking to an abuser

I'm so anxious right now, and I feel like a zombie. For the past 2 years me and my boyfriend and all of my friends have been fighting with this one guy because he's an abusive fuck. He sexually abused my boyfriend and my other best friend, emotionally neglected and abuser her, manipulated her, and then manipulated/catfished me in order to get my nudes. Somehow, after all of this, my boyfriend wants to "forgive" him and reunite with him. I'm so done with it. This has turned me into a stressed out, depressed zombie. I haven't felt like this in a very, very long time. I don't want to talk to my family members, play games, do homework, nothing. I'm so stressed out. I don't know what to do with my boyfriend. He's cheated on me twice now with this abuser, and I'm terrified he'll do it again. He's also been sexually abused by him too, which I just.. I don't want it. I'm tired of it. I feel like all the time I spent defending my boyfriend is going down the drain. I've come up with only a few options in my situation that I can possibly think of: Either leave him and let him do as he pleases and wait until something happens; Stay with him and let him do what he wants, but with strong boundaries; Or convince him to not even talk to this person at all. I feel like my best bet is to tell him not to talk to this person again and just leave the situation alone, or if that doesn't work I might have to leave him...For my own sake. I don't know I'm just so stressed out. This is hurting me so much, and I don't know what to do.