That fear of what he might or might not do shouldn't stop you. Sooo many men use this threat as control. He knows you wouldn't want this.
Don't think of it as him dodging maintenance.
Think about the financial freedom you will have.
At the moment you have no savings or your own income. Leave him and you will be financially better off. You will have an income from UC, and you know what, until he sees your not bluffing maintenance - remember you don't need to wait until divorce to put in a claim.
Then let's talk about the divorce. He thinks it's all his, all the savings, the pension, the house etc. The reality is once he put a ring on your finger, it all became both of yours.
I know its scary the thought of going it alone. But trust me, you and your children will be so much happier. It's really not a cliche. The weight that gets lifted from your shoulders. That dark cloud constantly hanging over you goes. Yes it takes time, but you have the strength within you to see that this isn't the life for you or your children.
At times you will feel alone, but remember you aren't. You have people in your life I hope that can be there for you to help you proactively. If not you always have mn.
There will be times when you question if you are doing the right thing. Just remember all those times you and your children have gone without whilst he's spending £££££.
Remember that feeling you have when you run out of money and you cannot ask him.
And you know what else? You will have your haircut and will have seen a dentist before the papers have been written. By the time the papers are signed, you will look and feel more amazing than you are now because you will be free and that confidence will start to show.
And karma is a wonderful thing. Start getting access to all the bank details now, and save all the bank statements somewhere he cannot get to. Those will show he's been swanning off buying things, whilst transferring you a small sum which remains the same whether he's in the country or not.