My sons dad has had it explained very bloody clearly what I think about him, and how revoltingly evil and abusive he was in the 5 years since he left and slithered back under the rock he came from.
I saw him last yeAr for the first time. In the lead up he was all nicey nicey.
But nothing about him has changed.
He has no power over me or our son (he's never once bothered to make an effort to do why ds wanted, pit off meeting him TWICE when he'd driven through our town)
He still tried to manipulate me and even made some thinly veiled attempt at a come on.
He will never get just how broken and unacceptable he is. I also saw my mother in him some how, and a tinge of my dad. Both of which have had more than a good go at destroying my self esteem all my life.
It was very sad to have to give up on someone so finally. But it is the only option.
Just do it. Rip the plaster off and eventually it'll feel ok.
This is the time when you have to do what you have to do, rather than what you want to do. Your dc will be better than fine, just make sure you use the age appropriate truth and make sure they know that his treatment of you (and it would be eventually them somehow) affects and destroys you and that you literally have no choice.
I would also say to them that the only chance he ever has of changing his behaviour is by you taking this action. Nothing short of this.