I just want to thank everyone for your wise advice. I was gone all yesterday after I first posted this, so couldn't respond until now. I am continually bowled over by the wise advice I get on this board. There were so many good suggestions. Thank you.
In answer to a few: the reliability of my husband's yes and no's is pretty good now, as long as I really take the time to explain everything carefully, which I did. However, his thinking is sometimes slightly off, especially when it comes to money, I notice. As far as does everyone know in his family about his opting out of ownership: I assume they do, but I guess I don't know for certain. It was a different sibling who manages this overall, and I think it was more her who he spoke with about it initially. But still, given the fact that he has been uninvolved in the cabin upkeep, etc., over the years since then, makes me think that everyone is aware of it. Also, donating to his mother's half instead: that is a good idea. We did send her a good-sized check at one point to thank her for allowing us to stay at her home, although she sent it back. She wanted to help us, and did not want us to pay her for her help. Can we afford to donate a little now, as a one-time gift? Yes, we probably can right now. Although our time of having "enough" may be nearing an end soon. We are draining our savings to cover rehab and college expenses, and soon will be living off of disability only, although we are fortunate in that my husband DID take out a good disability plan only one month before his stroke...