Well, following a diet that alleviates symtoms is a blessing, but it isn't a treatment.
And, despite the battery of tests you've undergone, have you had your stool tested for bile salts, or fat content? Or seen an endrocinologist to have pancreas tested? What are your common or current pancreatic enzme levels at? There are a number of people (I don't remember the %, but your doctors would know) who do have all of the outward symptoms of IBD, but never show any conclusive inward evidence of it. It just that there could be other issues at work here, and some with very serious repercussions, if left untreated. Testing for bile salts or fat content, etc., in stool is really rather nasty, hence a lot of Drs don't order/consider it. And the role the pancreas plays in the digestive system can cause a lot of problems similar to IBS or IBD, without apparent sign.
I shouldn't be harping on this, I'm no doctor. Just that I lost my dad to pancreatic cancer, and then I was mis-diagnosed with it, so i've been on a trail that thankfully not everyone goes on, and I'd hate to see something like that occur to someone else. Pancreatic illnesses can be very unforgiving at times, OK