He clearly needs to get properly diagnosed by a psychiatrist. He has all the hallmarks of someone with severe A.D.D. and possibly other underlying problems. He will NOT change UNTIL he's on proper medication and gets cognitive behavioral therapy. That's a multi-year road that won't show results until many months in.

What would I do in your shoes? If I still loved him, I'd demand he gets diagnosed, medicated and therapy and I might move on my own for a while and make clear he can earn my trust again when he shows that with treatment and loads of effort coming from him, he turns into someone I'd want to be with again. If there's a lot of prior conflict and all love has already been lost, I'd set him on the road of diagnosis, medication and therapy as a final act and leave when he seems to be in good hands so that I can really let go without looking back and wondering if the man I was with is lying dead in a ditch. That is all assuming he's not abusive, as in that case I'd just go.