Marina I'm so sorry. The words don't convey enough, but I truly am. Very sad and hard for you all.
I'm 2nd generation HD, but used to believe hoarding was defined only by keeping everything in chaotic squalor.
I'd always needed things clean and organized, but losing my twins months apart, then their younger brother shortly after the second one, and facing a great deal of suspicion, (genetic diagnosis many years later) was the start of not being able to let go of things normally here, as well as at times becoming excessive over cleanliness.
More tragedies hit later and the 'hang on to everything, save and repair things, organize them, and scrub everything' response was further triggered. Lack of money and stability exacerbated parts of it, but I was very unaware at the time.
However, no matter what may have triggered something, it becomes effectively irrelevant once the end result is ruining someone's life unless that knowledge can be used to create change. It's possible to care deeply and still be unable to live with something.
If this has run through winter and he's still not fixed it, I doubt he'd fix it after you went, so I'd put that into calculating the sale value of the house.
But, if you do decide to try and get what he's done fixed, then I wonder if in your circumstances it might be worth you or someone on your behalf, having a look at your local Round table organization and trying reaching out to them for help? You may find they have the professional ability within their group and the interest in assisting local community, and they may take a very much smaller sum if indeed anything, towards the work. I've seen good responses in the past when others who'd run into deep trouble needed local help.