duelling welcome and sorry you’ve had to seek us out 
Sounds like your stbxh has had a change in circumstances and that’s why he’s suddenly keen to get things moving.
Dropping maintenance feels like a very clear intimidation tactic to get you to agree to what he wants, I’d advice going to CAB to get list of solicitors locally that give free consultations so that you can see what you’re entitled to. You’ll probably find it’s a lot more than he offers you and wouldn’t surprise me if maintenance order gets put back up if he goes to court. Potentially you could keep living there until dc turns 18 too.
Unfortunately yes it is a fairly standard script that the betraying partner often says they are “being generous” but it’s all part of the bitterness that comes out during separation I’m afraid.
Also if there is no financial settlement through court you can always pursue him for pension etc at a later stage (and vice versa) so best to get that done too (I’m tying mine up as part of the house sale as xw is terrible with money and can see her spending it all on bf)