How many radiation sessions has he had so far? How much total proton radiation will he get? (During April-May 2021, I had 28 sessions of proton radiation @ 2.5 grays of radiation per session = 70 grays of radiation total. I had no fatigue, bladder or bowel after-effects.)

To answer your question —> it sounds like they’re overshooting his prostate and hitting his bladder & intestines/rectum with radiation. That’s not good.
> is he using a rectal spacer?
> is he practicing consistent full bladder/empty bowel protocol?
> is he remaining absolutely still on the treatment table?
> is he avoiding gassy foods?

As for concerns about a vacation planned after his last proton therapy, if he’s still experiencing those symptoms the first thing to do is for them to scope both his bladder/urethra (cystoscopy) and his intestines/rectum (colonoscopy) to see how much damage has been done.

The best way to manage these after-effects and how long they will last depends on the results of those scopes. If only a little damage there are OTC solutions that may work; if a lot of damage there are other therapies.