Rose Tiger is very wise.

Mine forced me to leave, to save my life, figuratively for sure, quite possibly physically. And he's found someone who seems pretty cool actually. So much like me--I can see both her intelligence and appeal and also the lack of self esteem. (I've stopped stalking her FB, though, LOL!)
He's not changed. When we must interact, it's still the same. He is treating her better than he did me initially, but that may simply be a different tactic. He WILL dysregulate. He WILL rage and manipulate her and scream at her. He WILL break things. He WILL cheat on her, to some degree or other. It might take longer, as they are not living together, but it will happen. And if she's smart, she'll leave--but it's not my problem.
It took me a long, long time to rediscover myself. To not have nightmares. To not miss him so badly. I began to realize it wasn't HIM I missed, but the feeling he gave me, and I am learning that if you seek that feeling outside of yourself--that completely safe, strong place where you are valued and respected--you always run the risk of losing it. If you can learn to give it to yourself, you will never, ever be alone, never be abandoned. You can't leave you. I'm working on that, but whenever I miss him, I remind myself of the constant "fight or flight" mode I was in--living in anticipation every second of "will this trigger him?" and the awful repercussions.
I'm only at the beginning of my journey, and I wish I had left him long ago. I'm turning 50 this year--hard for women to get back into the dating pool. But I'm not even interested in that now, because I want to start when I feel sure that I'm emotionally strong enough to be able to open fully and be OK with having it go away if it must. And once I get there--it's going to be great.
You will get there too. And you will really WIN. Whereas he never will unless he makes some enormous changes that he will, sadly, likely never have the courage to face.