@tbyota
I agree with others that suggested Decipher test. Also, he can ask for Prostox test that will determine his reaction to radiation. Some people are genetically more sensitive to radiation toxicity and can have higher incidence of long term side effects.
Regarding having surgery after radiation, it is actually other way around. Radiation damages prostate to the extent that it is almost impossible to remove it after radiation. Only a few surgeons have expertise to do it or are willing to do it. Many people choose RP because after surgery they can have salvage radiation if cancer ever returns.
Both RP and RT have the same success rates except in rare cases when pathology shows IDC or cribriform gland present. In that case RP has some advantages according to some scientific papers.
Regarding weight problem - I would advise that he tries to loose weight because weight loss is very important for long term cancer control since obesity is proven risk factor for prostate cancer. If he is not willing to reduce caloric intake and to start exercising program, maybe he can try Wegovy . I think that it is approved for weight loss now and especially if person has any cardiac problems.
Whatever you decide, I am wishing your husband super successful treatment and complete eradication of cancer < 3