yes contact women's aid for help getting him out. Your relationship with your three children and their relationships with each other (and he's also damaging those) are much more precious to you than your relationship with him. Don't sacrifice precious relationships for fear of the unknown or fear of uncertainty (financially). Sorry if I was harsh last night on my phone. It's a really shitty situation for you and I'm sure it came gradually. It's so passive aggressive as well, not speaking, that the extent of the "water torture" only dawns on you gradually, and then you feel you've lived with it for a while already and you seem to be 'ok' (just) so you feel it would be an unnecessarily dramatic move to do something as drastic as put your foot down and say no more.
I would say the damage is so extreme now, it wouldn't be enough for you to just say "start speaking to the children now or you have to leave" because that's sending a message to them that they're back in favour now. And you had to 'negotiate' that on their behalf.
I think if I were in the shoes that your children are in, I'd want my mother to pick me, pick us.
If you value your relationship with your children, speak out now. You have to (literally) choose them. I wouldn't waste time asking him to apologise to them. I would get him out of your home, YOUR HOME ffs, the children have had a parent in their 'home' who doesn't speak to them for years
and I would say to them 'he's gone now and I'm so, so sorry that I wasn't strong enough to take this stand earlier'.
Your children need to know that you SEE that his behaviour is wrong and they also need to see that you're prepared to make a stand.
Sorry if that sounds harsh but sometimes lookinng back on things that hurt you can judge the people who stood by and didn't nail their colours to the post. more harshly, because it hurts more.