Sorry one more thing about staying friends.
Would it ever really be a friendship? Even with my friends, I expect some sort of reciprocal support. It's a two-sided thing. With an ex like mine and yours, would it ever be that?
For me, I know that if my ex and I stay friends, I would still be committed to him, while he would take advantage of that support without giving anything in return. It's not really a friendship. After everything he's done, I'm sort of at the point where I need to just stop trying to understand, stop trying to have contact, forgive him, move on, and don't look back.