You should not carry on like this for goodness alone how many more years. He will destroy you completely if he is allowed to do that to you.
Do you not think you and your children here have suffered enough?.
He is not a good dad to his children if he treats you like this, women in abuse situations often write such comments when they cannot write anything at all positive to write about their man. You have done precisely this in your post.
This is already affecting your children and markedly so, this stuff can last a lifetime. Your son is already copying how his dad behaves towards you, he is learning from his dad that this is how you treat women (there for being abused and as a possession).
What do you think your children are learning about relationships here from the two of you?.
Your children are already learning a lot of damaging lessons about relationships, lessons that they could well carry forward into their own adult relationships and they could go onto be emotionally abusive themselves. You simply cannot protect your children fully from what they are seeing and hearing at home; this is no sanctuary for them either but a warzone that they are also caught up in.
Why do you think he would even get 50/50 childcare?, such is based on pure supposition and not fact. Do you think that such a man would even bother wanting his children half the time post separation anyway?. Such men only think of themselves ultimately.
You need the help of both Womens Aid on 0808 2000 247 and decent legal advice to leave. You cannot go on like this and staying any longer within this will make it harder for you to leave because you will be further ground down.
This is no legacy to leave them and any supposed fear of being on your own is trumped by the fact that your children are already being harmed emotionally. They are being damaged by their dad's private war against you their mother.
It is hard to leave but taking the first baby step to leave is often the hardest one to make and do. Also fear keeps you within this. However, no obstacle is insurmountable and no person is above the law.
Call Womens Aid and take that baby step out to begin a better life for you and your children.