The side affects you describe of his surgery, ADT, and radiation sound about "normal." Some of them such as weight, muscle, can be addressed through diet and exercise.
Your medical team should be able to discuss with him ways of mitigating the hot flashes, notice I did not say eliminate.
If he is not seeing a cardiologist, consider adding one to your medical team given the known cardio vascular side affects of ADT.
If he is still on ADT, consider asking your oncologist or urologist about intermittent ADT. It may be possible to stop, actively monitor and then restart treatment based on clinical data such as increasing PSA, imaging…
As to the sexual side affects, particularly from non nerve sparing side and ADT, well known and a challenge gto reinvent intimacy.