I need a serious second opinion in my situation with my partner. (Open my eyes)?

First from what I could gather it seems to me this guy isn't done with his ex and until that happens you should definitely not get involved. You don't want to be the rebound person, I would move on. But I think you made some typos in your post and you may want to re-read it and add something as way of explanation, because it was a little hard to follow. I hope that helps.