Argh, I am so very sorry, didn't realise how long this was (sleep deprived) - what a thread to do that on. 
You are being SO BLOODY BRAVE. Hang on in there - this is the final stretch to freedom.
Firstly this man knows you. Of course he hasn't truly written you out of his life - he is saying what he knows will hurt you as badly as he possibly can, plus guilt trip you, as a way of punishing you for stopping his control and abuse. He's trying to punish you emotionally because you finally made consequences attach to his physical abuse. You can't report him to the police for emotional abuse. He is talking utter and complete bollocks - if he didn't care he'd not be saying this crap at all. He'd just be bothered about seeing the kids. He knows you and knows what buttons to press and is ramming as hard as his porky little fingers will let him. Those words are NOT about forcing you away at all. He's trying to scare you into thinking he doesn't love you any more, so he can reel you back in. It's a game, to reassert his control over you and over the relationship, by smashing your new-found resistance and independence down. That simple. You were so emotionally dependant on him and he was so inside your head that his threatening to abandon you is still frightening, right? And he knows it. A classic abuser line, when being nice, is "what would you do without me, hey?" chuckle, chuckle, hug, "you're hopeless." Drip, drip, drip. And he is pressing his nuclear option because that's all he has left. That and the fact that self-pity and a powerful sense of entitlement are also abuser traits, and your DARING to challenge his control over his property (that would be you) will trip those, too.
As for "ultimate betrayal" - what, getting some protection against his violence is a betrayal, while him beating you is not? My God.
Please don't let him have the kids until you have some sort of legal arrangement for residence etc set up. You sound like you still think that it is YOU that is triggering him, "making" him be this way, rather than who he is, and would be no matter who he was with. I do not think you can be so certain that he'd not harm them, tbh, because this is not about you - the lack of remorse, blaming the victim, psychological terrorism, emotional abuse is too systematic. There is also a concern that he might just refuse to hand them back, surely? For a loving mum that would be pretty punitive, and he has to know that.
Please don't feel alone. You aren't alone. You can post here any time and we are all real people, just in different parts of the country. If you need a voice at the end of the connection Women's Aid will help. I do think talking to women who have been there, got out, and built happy and rewarding lives in freedom will be a huge support, no? And there is your Mum. I so hope you've told her what you've been up against, by now. You need a bit of mothering, IMO. Wish we lived in London, or even near, because I'd tell you to come over to mine.
Hang on in there. You can't get brainwashing like you've been subjected to wiped clean overnight, but you've made a phenomenally good start. I think you are very, very brave. And one day, reading all this back, you'll be as awed by your younger self's guts as I am, now.