I think get a piece of paper and start writing up your situation now, you and the kids, your studying. Outgoing and incoming. See how it all stacks up.
You need to take complete control.
If he won’t show you a credit check - sign him up for it if he hasn’t got it. Then you seriously need to separate yourself financially, which means move separately even if it’s temporary.
If he does show you it, get two bits of paper.
One for staying with him. Go to citizens advice or online budget calculator.
One paper for on your own. Look up benefits calculator online and pretend you are a single person. Jot up all you are entitled to, and write these down very clearly. Again, budget but this time as a single person.
Do this even if you are adamant you are to stay together.
Then have a good look at both bits of paper. Project 1, 2 and 5 years into the future with each financially.
Talk openly with some people you trust. Bear in mind the finances.
Think about the emotional toll too, he depends on you emotionally and financially. Then start thinking which future your CHILD needs.