As far as meds go, this one is not too bad if he had to be on something long term. Weighing chronic diarrhea vs. Centrine - the diarrhea would be way more damaging, hands down.
If the drug does the trick, your diet options could be wide open - esp. with some of the supplements you're already aware of, which will be needed to heal his digestive tract.
If the drug doesn't do the trick, if it were me - I'd then go the route of homecooking whitefish, potatoes, greens - and/or contact Susan Davis at askariel.com.
