Most Helpful Girl
Follow your gut. If he was engaged to this girl, that means at some point in his life, he wanted to spend the rest of his life with her. She ruined everything through cheating, consequently wounding him in the process. Unfortunately, your guy is still emotionally unavailable. It sometimes take people a while to get over such situations since its something that betrayed trust, love etc.
You're smart to take a break. Some people try to move on and suppress feelings thinking they can just get another girl, and life will be fine. I dont think this is the case. I think he is trying to move on, but he is hurt... STILL. And I believe that us evident if he is not completely present in EVERY way in your relationship.
If I were you, I would put an end to things for good. It sounds like he needs more time to himself to heal. Good luck.