I have no idea what causes chronic pouchitis, other than bad luck. I think that making up stories about it is likely to do more harm than good.
I eat just about anything and everything; I guess I limit spinach consumption, and choose smaller salads than I might prefer. My bathroom usage is just about perfect for me - properly treated pouchitis just looks like a well-functioning pouch. I did try a very-low-carbohydrate diet for a while, since some cases of pouchitis seem to respond to that, but I didn’t experience any benefit from it.