WIBTA for taking advantage of my boss’ possible manic episode?

I know this already sounds bad but hear me out.

So I (30M) am the sole employee of this guy (62M) who’s honestly just a miserable boss and an even more miserable person. It sucks so bad working for him—the pay is horrendous, he’s verbally abusive, and the working conditions are awful (in the winter I literally have to stay bundled up the whole work day because he refuses to put the heat on in the office). He wouldn’t even give me holidays off if it wasn’t for the fact that there’s basically nothing to do those days because everywhere else is closed. I’m almost positive he unironically thinks poor people should die if they can’t work. His nephew (aka his only living relative and just the nicest guy) came by yesterday to invite him to Christmas dinner and he told him he’d see him in hell.

I cannot stress this enough—it’s BAD. I’d quit, but it’s been hard finding a better job and I’ve got four kids at home, including one with special needs.

Anyway, so here’s where I’m wondering if I’d be the asshole. Today was Christmas Day and he showed up at my house out of nowhere (huge red flag, I know). At first I thought he’d forgotten I had the day off and he was here to chew me out, which was worrying enough, but then his whole demeanor changed and he was super happy and excited and talking about how he was going to raise my salary. He even mentioned possibly making me a partner in the firm.

Now if that was it, I’d feel a little weird about the suddenness of it but it’d be fine. I’m not going to complain about having more money to feed my family. But then he started talking about how he wanted to pay our mortgage off. He talked about wanting to pay for our son to get the very expensive medical care that’s probably going to save his life. He mentioned at one point that he was going to be donating a huge amount of money to charity too—I knew he was rich but it staggered me. All this from a guy who doesn’t (didn’t?) even want to turn on the heat or the lights because it costs too much money.

It was such a sudden and drastic change that happened very literally overnight and now I’m kind of concerned he’s having a manic episode or something. I really, really want to accept his sudden generosity (I probably will; my wife is all for it and thinks he owes it to us), and I would love to believe that he’s truly had a sudden change of heart (an actual Christmas miracle lol) but I’m just worried about the possible consequences of accepting huge financial gifts like this from someone who I believe might be experiencing some kind of break from reality. Even if there’s nothing legally wrong with it, I’m worried about the ethics of it.

TLDR, my asshole boss might be in the middle of a mental breakdown. WIBTA if I accepted his offer to pay off my mortgage and my son’s medical expenses?

Update: I got the courage up to ask him about his sudden change of heart while my special needs child was napping in his lap (what), and he told me he was visited by three ghosts. So. Definitely not well. Still not sure I won't take the money.