Hrm...the way I see it, here are the facts (taken from what you've shared):
1. You are in a toxic relationship.
2. He is verbally abusing/trying to blackmail you.
3. He is emotionally abusive to your autistic son.
4. It doesn't sound like he will let you go without a fight.
With that in mind, I would agree that you need to get yourself and your children out of there as soon as you can, and it would probably be the best thing to do for their sake as well as yours. There is a huge difference between what he SAYS and what he DOES. He says you can split amicably if things aren't working out, and yet he gives you very few options for leaving. Is an order of protection possible?
Honestly, this sounds like a potentially very dangerous situation. Do you have friends/family nearby you can count on? People who can protect you and your children? Have you spoken with your lawyer since? A women's or family shelter may be good place to go if you need to get out fast, since applying for government housing can take months (those waitings lists took forever even when the economy was good). I'm glad that you're set on getting out of there, and once you do, you will have done both yourself and your children a great favor.
I certainly won't criticize you for your past (what's past is past), and I certainly won't criticize you for remaining in this relationship for so long (it happens quite often). And I will give you full credit for finally saying, "Enough is enough." You may have loved each other once, but real love isn't supposed to hurt or manipulate, and he will continue to hurt you and your kids for as long as he is allowed to. Neither of you has been 100% innocent these past 9 years, but abuse is abuse - let's call a spade a spade here. And I will give you full credit for saying enough is enough.
My best advice is to get you and your children out as fast as you can, any way you can, because he will continue to hurt you for as long as he's allowed to do it.