I know you are angry, your post title states that. So please don''t take this the wrong way, it is meant as a neutral comment and I am assuming various things, namely that your ex got nothing from the sale of the
marital home and it was indeed the marital home.
If the above is true, I think you got a fantastic deal. Having looked into deeds of trust myself to protect my assets when remarrying, I was told that once you marry they carry very little weight in law. The basis for English marriage in law is that all assets are shared, regardless of where the money came from. There are several other threads on here with people trying to protect inheritances but the courts do consider them fair game. That you were able to honour your deed of trust is great, but I imagine your ex could have made a claim to this if he wanted. You say you worked part-time to bring up the kids, your ex might say you could only do this as he was going out to work and bringing in money to pay the other outgoings.
If your ex did get nothing from the sale then his outgoings in all likelihood will be very high. It costs a lot to start again when you rent or need to find a deposit.
Your net income is 17k pa, with no mortgage. His net income will be around 24 k ( after tax and maintenance) but he has additional housing costs. And, unless you forgot to mention this, he has no significant assets.
I think that you did get a very good deal and I would try to get this formalised ASAP before your ex changes his mind.