What Joie said.
It is on your man to get appropriate chiropractic and massage therapy and maybe PT to get him exercising again.
It is on you to say you can't risk your health in providing that, and further, that you need him to lose weight or at least stop gaining it.
Moving on from someone who won't address morbid obesity is valid. It's understandable not to get turned on by someone whose, uh, lil someone is hidden under multiple belly folds. Who is just "oh well, he's not not working. How bout a massage?" Yeah, I had that happen, too.
Relationships include physical compatibility, and you aren't asking him to be 30. Just not to be gross and demanding.