So he saw you blocking him as selfish, and you wanting space and peace.
Instead of allowing you that, he stomped his way in again and made sure you wouldn't have either of those things.
He is the selfish one, Pithy, as he has been all along.
A loving, caring partner wouldn't need you to have to explain their selfishness to them. And if you did have to, they would then act on it.
He didn't.
After you talked to him about things in your relationship you were unhappy with, he did - nothing. He changed nothing.
His kids still ran wild in your house, causing mess and havoc.
You paid for the cleaner to fix that. He didn't.
He still didn't go for walks with you, he gamed.
He couldn't be bothered to bring you a coffee in the mornings any more.
He called you a c**t.
Yes, it's like a bereavement. But the loss you are mourning is the loss of what might have been, if he had been a better man. A better partner.
What you had with him wasn't enough. It wasn't making you happy, in fact it was causing you (and your son) stress and sadness. That's why you posted in the first place.
Remember that.
Make sure he's blocked on everything.
And give yourself grace as you move through growing into this new phase in your life.