I have a bad back and despite my limitations could spend months in parks and not see everything. Back problems vary from person to person. I can ride Splash Mountain but someone with poor upper body strength it would be too much. I miss the Bobsleds at
Disneyland and could ride it all day but for some people the sideways movement would have left them in tears.
The autopia cars are fun but for me only if I have at least two friends behind me to protect me from rammers. Bug's Life is a fun show but one point you get poked in the back and that hurts me as well as scares me that my back will get poke in the bad spot. I rode the WDW version of Pirates and was videotaping when the boat screeched to a halt and I nearly took my eye out.
In summation there are obvious ones to avoid like Dinosaur but if his back is really really bad then even some simpler rides might be off limits. Read the board for trip reports by people who are wheelchair bound thus not being able to ride almost anything as they will show you all the possibilities out there.
You married him for better or for worse, in sickness and health, poverty and wealth until death do you part. Right now he is low on health and things are a bit worse but dont ever let that stop your enjoyment of life and each other. WDW is designed so that even those with poor health can have fun. There are shows, exhibits, dining, people watching, games, parades, fireworks and so much more.