There seems to be too many red flags and your distrust in HIM is valid. Cheating on someone isn't a conversation you have by "promising" you'd "never cheat". That, alone, is a red flag. I've never cheated on anyone in my life. I don't have to promise my partner anything. It's just not a "me" thing to do.

I don't think there's anything he'll be able to do to rebuild that trust in you. He has tendencies that one would be concerned about, not just you. We all have a "good" side. It's really more about how low we allow our "dark" side to lead us. So far, he's gone pretty low.