Poshgirl, I'm sorry about your situation. It seems like so many of us are in situations with unwell loved ones, and it's almost like we are forgotten. No one is going to do for us, we have to do for ourselves.

Beth, you hit on something that I was thinking about- something that resonated with me previously. There is no way to know why his relationship with his parents is a problem for his wife, but I also relate a bit to your situation. My husband's family is heavily enmeshed. My boundaries haven't always been great, but they've been better than the ones among his family members as a general rule. Dh has to enmesh with someone- looking for external validation. When he felt like he wasn't getting what he needed from me, he emotionally abandoned myself and daughter, and reenmeshed with his family of origin. When he interacts with them for an extended period of time, it often means trouble for me. I think he wants that unwell relationship with me and is struggling to force it to happen at times.

From what RD has posted, I doubt his situation is like that, but her perception could be of a place of abandonment, of not belonging to the group where he seems most invested. There are obviously a lot of moving parts and reasons that can be good or bad, or both.