You can do this OP. 
Is he locking you in the house when he goes to work on nights?!
If he is giving you keys in the morning can you get another set cut without his knowing.
Or if he is leaving you without keys so you cannot lock the door to go out just go out leaving door unlocked.
I had same problems as you with exh...he was an evil son of a bitch but I did manage to leave and I took the car which was in his name.
He kept both sets of keys for house either locking me in or leaving the door unlocked so I could not keep myself secure in my own home.
I went to a friend's that he did not know about and he spent the whole weekend trying to find the car as he had a set of keys as well... but he never found it.
He did convince me to go back after a few weeks but only because he wanted to put me through more hell and that's when the real physical violence started.
By the time he had finished with me I was suicidal and felt worthless but something in me just made me realise that if I did not leave soon I would probably not survive.
The last and final time(5months later) I left.
I had stacked boxes in the garage saying it was stuff that was going to be collected by a charity shop I had been doing it for a few weeks on the pretext that I was going to start decorating some rooms and was decluttering!! I started painting one of the rooms to make him believe I was working on the house.
Actually it was collected by removal men(I knew the man who owned the business) in an unmarked van at 8.30am...
and I was in my pyjamas outside giving them a set of keys to the new property I had rented in another town....I borrowed over a £1000 from friends to get the house. My friends were absolutely brilliant.
I then waited until he went in the shower (usually around 9am as these bastards always have some sort of routine) and got the 2nd set of car keys he had hidden(which I had found in his wardrobe and I left there so that he thought I hadn't found them). I kept checking that the keys had not moved.
I put the dishwasher on and set his coffee pot going so there was noise in the kitchen.
Opened the kitchen door and left it wide open.
Went in bedroom put pair of trousers over my pyjamas and left the house with my handbag and another bag from the wardrobe that I had packed for a few weeks so it didn't look out of place and took the car as he's still in the shower!
Any other stuff that was left I never went back for any of it even though he kept leaving me messages about it!
I drove to meet the removal men at my new property.
My friend then came the same day and helped me leave the car on a country pub car park about 3miles from his house with the keys inside and I texted him the location and that was the last time I contacted him.
I went back to a peaceful life in a town 15miles away safe and secure behind my own front door.
I bought a new mobile and phone number and never answered the old one again and he left hundreds of texts and voicemails some abusive some nice. But I never answered any of them.
I changed my name by deed poll.
I did not leave my new house for 6months. I was in a real state of stress and could barely function but I knew I would get better even if it took a long time.
So sorry for the long post but .....
The reason why I am writing this is to help you realise that even though he may think he's smart, you are smarter and you know his behaviour and you can use this to your advantage to form an escape plan.
Just try and keep calm about it all and channel your nervous energy in saving you and your children from the evil bastard!