Sigh. I'd had other plans for what I was going to do on the computer this evening, but when no other "advocates" responded to the post, I had to do so. I'll share here what I said, with an added footnote:
[Person], speaking as an autistic we're wired to show emotions very differently, and it's an old myth that we have none. (As one of us* wryly put it years ago: we can't read non-autistics, so they think we're unable to read anybody; NAs can't read us, so they assume we're incapable of expressing anything.) My father's autistic as well, and while we can seem enigmatic to non-auties, we have no problem sensing one another's feelings.
I can easily understand your father staying & taking care of your mom after she became severely disabled. Most auties hold very tightly to the ideas of right & wrong we learned as kids, to the point that how someone else acted towards us is often irrelevant. The right thing to do, if one's partner becomes severely disabled, is to take care of them; the wrong thing to do would be to use it against them or leave.
I keep bookmarks for educating folks on autistic minds, I'd be honored if you use them to understand your dad & other auties in your family:
I hope you have a great week!
*The person that made the wry observation was Frank Klein. He ran a wonderful site of personal essays, which is now only available through the Wayback Archive: Autistic Advocacy.