I do not think calprotectin has been as closely followed in J pouch patients as with those with a colon, so it's hard to truly know what the number correlates within our population (last I'd read; it can be a guide, like Jan said, with other symptoms... not sure the significance faced with good other results).
van, also look over the FODMAP diet. It helped me to do the elimination then the reintroduction of the different sugar groups, to find bloating triggers. Goes along with managing SIBO, which is small bowel overgrowth of bacteria; sugars can feed the bacteria and cause symptoms. Antibiotics can get it under control, but knowing triggers can help you avoid food that causes worsening symptoms.
I do believe there is a breath test perhaps for SIBO (I don't know much about it), but often it's dx just by symptoms when pouchitis is ruled out.