had kind of a similar experience many years ago, as the middleman/designer between the maker and the buyer, for a similar amount of money. Things were going really well, until the deposit was paid, then the excuses started coming....
in that case, it wasn't even my money, yet the whole thing- which started off with high hopes and no worries about the little things- was extremely stressful. On the one side, I had a buyer who wanted their money back after things went pear shaped, on the other, I had the maker- who'd subcontracted part of the job- threatening me in various ways and laying all the blame at my feet.
I'll never forget that feeling, which is a good thing because it's a lesson I do not want to learn again!
after all the foreseeable foot dragging and excuse making, the buyer was eventually made whole. Nobody came out of that situation better off, if you don't count hard lessons as a benefit.
it doesn't sound to me like this situation is going to be book ended by some resolution, and even if the money is repaid, you're still being stiffed for your time and energy. I can only imagine the sense of optimism and promise you must've felt when first entering into this agreement, and the real loss here is how thoroughly destroyed that hope and optimism is. That's something that'll be hard to get back. And I'm not saying that it's wrong to pursue this matter by any means, but it's important to point out that you've lost something more than money here and it will be solely up to you to figure out how to get that back.
I hope that, for your family's sake, you get made whole financially. And for your sake, that you are able to move on from this without carrying too much baggage going forward.