Not sure of the whole situation. However, I am going to respond to your message with the insight of someone that has gone through medical issues and had parents that did also. The cause of my medical issues is not known.
My teenage son has said how he is glad that I haven't made everything about my transplant and health. Most of the time I discuss other things depending on who I am talking to. I am an Elder with my church, so often discuss the administration of the church with other members. I am one of those people that pray for everyone else and only discuss my health issues when asked or to say thanks to God when I get positive results or to let people know I really can't talk at the moment due to being at the hospital. When I was at my worst, I was still telling people that I was ok, even though I couldn't speak a full sentence without being out of breath with 5 liters of oxygen. I try to be more involved in current topics and how others are doing.
I also know that with my parents, us kids got annoyed with my mother because she would make food that was not on his diet (diabetic), which caused other issues. My mother would say that he doesn't like things that were healthy for him. When we gave him other foods that he were on his diet, he liked them.
DH's kids could believe that whoever is doing the shopping and cooking is not buying or making healthy choices. They also might feel that all that is discussed is medical issues and there is no interest in what others are trying to discuss or their interests. I know that my mother would start this and we would steer her to other conversations.
On another note, I am not sure if your husband can have acupuncture. Years ago, I had injured my back (twisted the spine) at work. No matter what I took, nothing would get rid of the pain. I was at the point that I could barely walk and people would want to help me. I went to a DR of Chinese medicine. He performed acupuncture and cupping on me 3x a week at first, reducing to once a month, until the issue was resolved after about a year. I would also receive therapeutic message. He was able to straighten out most of the spine and the pain was greatly reduced after the first month or two, and now I have none. I tried a chiropractor, but it didn't do anything for me but works for others. DH might might want to try acupuncture, a chiropractor and/or therapeutic message. It's none invasive and works for many, but can be expensive.