Hi Starting,
Been lurking on your OP and this one too. Jeez you've had a rough time.
Went through something very similar myself a few years ago. A lot of what you say about your ex reminds me of mine, esp the mercenary attitude towards getting money out of you.
I ended up paying mine off, with a small sum (as per your situ, the house was mine) to a) get him off my back and close a very painful chapter and b) to avoid legal costs. With the benefit of hindsight I'd definitely have sat back and gave him nothing - and let him go through the whole legal process of getting money out of me.
If it's any consolation you will look back on him in a few years time and smirk at how embarrassing/low he was for desperately trying to scavenge what money he could get off you. That's how I feel about my ex now.
I just wanted to offer some words of encouragement and say you're doing really well and should be proud of yourself for getting through such a tough time.
The future will be brighter and better, and one big positive to come out of this is you will change forever, to a stronger woman :-) I know after it happened to me I didn't take anything for granted again, appreciated life's smaller pleasures much more and as a whole became kinder and more empathetic.
Keep doing what you're doing.
Best wishes x