I don't have a j pouch, but I do have a regular old ileostomy.
I agree with walking... as bad as it may hurt to stand upright when you are in pain, it really does help "move" things along.
Is he by chance, drinking sodas with his burgers and corn dogs? Many times, sodas can cause a lot of gas that can be painful. Even a person w/o an ileo can get gassy from sodas.
Staying well hydrated is important. Does he like gatorade? Or anything else that is not carbonated? Ice tea can be a diruetic, like coffee. I like cranberry/black cherry juice but I mix it at least 50/50 with water. Cranberry is good for the kidneys, etc. too and tastes pretty good with the black cherry juice. Be sure he is drinking plenty with his meals too. Maybe the food is tasting so good that he forgets to drink enough with his meal... been there, done that!
Keep your chin up. It's like fine tuning a car. Once you get it figured out, it runs smoothly. There should be a manual for every single human being so we don't have to figure this out on the fly! Keep in touch,