Sorry, Jen but this made me laugh. I had something similar in my divorce... and you know what? Bossy, irritated, controlling A's can be put in their place by very few people - but a JUDGE is one of them. When faced with going to jail or a contempt of court charge/fine the A will often "see the light" and sign the paper. OR, in my case, the judge's signature overrode the lack of my A's signature.
That's a lot of money to walk away from... are you willing (and able)vto spend money to keep some, or is it better to just walk away?
The other thing you could try is to have your ex sign something say he has no interest in buying the house and couldn't buy it for a period of time even if you had to list it "as is". That would force him to show his "plan" .
I'm glad you're able to think clearly and are moving forward . I'm thrilled about the Rocking C and can't wait to see pictures!!
Hugs
Cats