If one of your own children as an adult came to you with this problem what would be your advice?. Would you tell them to stay?.
All your words here are words that an abused person would write. You only need to give yourself permission to leave.
Its not you, its him. This abuse of you and in turn your children who are and will pick up on all the vibes here, this is all on HIM. You did not drive him to abuse you; he chose you to abuse and deliberately picked you out. You were vulnerable from being abused yourself and he has further exploited that vulnerability. He has abused your trust in him totally.
Your own troubled background played a huge part here in leading you to this man because its an extension of what you already know. Your own boundaries, skewed by seeing abuse as a child, are being further eroded by this man now. No-one ever bothered to show you what a mutually respectful relationship is like and this is certainly not a respectful relationship you are describing. You've been with him 20 or so years now and my guess too is that he has ramped up the power and control against you over that period of time. He likely ramped this up too against you after you were married and again when you became pregnant.
Look at what you learnt about relationships when you were growing up?. Now come to present day where your children are learning similar sorts of lessons. They are seeing him bully you and you appeasing him and being acquiescent in return. That is no legacy to be showing them. You have a choice here re this man, they do not.
Has your counsellor called your H an abuser?. How honest have you been with this person re your life at home now?. I ask only as abuse like you describe thrives on secrecy and such victims of this crime do try and cover it up and or otherwise put a brave face on as you have done. You need to stop with ignoring and otherwise glossing over his abuses of you. Doing that whilst you are all under the same roof is impossible.
As for your supposition that he may want 50/50 he likely would not. Such a man is not bothered at all with his children if he abuses you as their mother. Its often only stated by such men as a further threat and attempt at maintaining power and control over their chosen target i.e. you in this instance to keep you in line. No matter how you act he will and indeed is moving the goalposts around.
I would certainly recommend you contact Womens Aid in your circumstances. They can and will help you here escape your abuser because leaving him is your only real option open to you going forward. He won't change and you've never driven him to abusing you. He has done that because he can and he felt entitled to do so (as did your family of origin as well). You've never triggered him same as you never triggered your family of origin.