Just in case no one has suggested, he sounds like a good candidate for semiglucatides. (Ozempic, Trulicity, Saxenda).
It’s a mini jab you administer into your gut or thigh every week (or sometimes every day) and it helps reverse prediabetes and reduce the impact of diabetes 2. For the majority of patients it has an amazing impact. The main issue is that you have to push on through teh first 6 weeks because you can feel very nauseous, but he could also be given something for that.
I know it’s difficult to get hold of because it’s expensive, but maybe you can get him to the doctor by saying it’s literally a magic bullet.
If he hasn’t tried that, he hasn’t tried everything. Bariatric surgery has so many long term effects. Since getting a weird thyroid problem, I’ve discovered thousands of post-surgical people get massive problems that are triggered by imbalances in calcium, magnesium, vitamins etc. not as easy as saying malnutrition, but ending up with kidney problems, liver problems. And tons have exhaustion from these and hormone problems (meaning thyroid etc, not sex hormones). Not in the first 5 years necessarily, but in 10, 15 years… so it’s just delaying the disability if you like.
I woudl say undoubtedly his prediabetes has returned, and probably now diabetic, given that he is feeling so unfit. But anyway, if you can’t get him to the GP and get a serious answer from them, then I would consider the leaving.
TBF, I think the weight is a side issue too, if you’ve always done everything, he’s not going to start pulling his weight (so to speak) now, is he?