I haven't read the whole thread but wow!
"How do I make it stop"
You can't, you can only leave him, only he can decide to change and that doesn't seem likely now does it?
"no where to go"
You find somewhere for your kids sake. Women's refuge, speak to council, parents, friends, rental. Think short term then long term after.
"can't face sharing the children with him"
You should already be doing this in an equal marriage he should be looking after then too they are also his kids. If he doesn't look after them now doubt he will be bothered to if you split.
"scary to cause huge upheaval"
Scarier to live with a man who treats you like a worthless piece of shit and thinks he's owed sex, what kind of role model is that for your kids and their future relationships. It's not going to get any better, it might just get worse.
"don't earn very much"
There is more you can do about this if you are willing. Start looking into what benefits you could receive as a single mother. Would a career change help. Is there training you can do to further your career, will an employer fund it for example some NHS, teaching? Can you get free advice from the citizens advice bureau and online. Is there help with childcare you could find so you can work additional hours to top up earnings? Change jobs in your current field or opportunity to work your way up? When you leave he will still need to contribute towards his kids financially and you can go for CM depending on settlement.
"he might stop being mean one day"
Very very unlikely when it gets him what he wants or he is just a nasty person. They don't usually have an epiphany unless something drastic happens to give them a shock like their partner leaving them and even then it's only usually short lived.
"scared to tell people"
Is it really easier to live a lie to keep the status quo with someone who doesn't love or respect you and be abused until he one day cheats on you and leaves you anyway? Do you think people wouldn't support you and if so why not? Most people if they are your friend at all will support you. It's more common than you think, something like 1 in 2 marriages break down. It's not a reflection on you, you haven't failed. But failing to act now will have greater consequences for you and your children.
"Scared he'll bad mouth me to children"
If he does this it will reflect worse on him than you. Kids are smart and will realise this. It's not nice to be around a parent who disrespects the other one. What's to stop him doing this now anyway as he clearly resents you, how do you know he doesn't or won't in the future married or not?
"Sad that our marriage will have failed"
It already has. He doesn't love you and is showing you this by his treatment of you, be sad about that now. Eventually you will be over it and you will realise you are better off without this sex pest arse. What exactly do you think you need him for other than financially (which can be fixed!) It doesn't sound like he helps out with the kids or other things?