Help with ex husband

I already asked around this, but in a different way.

I have a model around my ex-husband’s abusive behavior towards me and I keep doing models to try and feel better or get perspective. I loop on this one a lot.

Unintentional model:
C – Ex-husband did and said things
T – He should not have done those things to me
F – Unloved
A – I look for more evidence for his lack of love
R – I find a lot of evidence for his lack of love

Intentional model:
C- Ex-husband did things
T – Maybe I had to go through that to get where I am now
F – Slightly more empowered
A – I get curious and do a lot of models to get perspective
R – I feel a little better

So, my question is this: I can make myself feel better about the situation in a spiritual sense (“I had to go through hard things to get where I am going type thing”), but do I let my abuser back into my life?

He says he wants to be friends and co-parent amicably, but every time he does this and I agree, he reverts back to his abusive ways with me within a short time. I don’t want to keep falling for this.

The thing that is extra hurtful is that he is apparently very loving and doting with his new girlfriend, but he treated me like a whipping post. He was abused as a child by his father and then I think he took it out on me and I became his punching bag, but not this new girl. I think he has evolved a bit and realizes that he cannot act like that, but I can’t undo what he did to me. I still have nightmares. I never did ANYTHING to deserve his wrath… I don’t want to keep giving him my power. I am so incredibly hurt by him, but I don’t want to feel this way anymore. I cannot seem to get out of this loop and it is taking up all of my brain juice!!! Help!!!!!