Side note: My theory for this was that my eating habits would periodically put my microbiome into significant stress, which would cause a terrible episode of intestinal inflammation after eating.
I don't know what your inflammation was from, but Crohn's disease wouldn't surprise me. It's a hard diagnosis to make. I know two young, otherwise healthy 20-somethings who had Crohn's and the pain you describe, and both of them had to have much of their colons removed.
But encouraging research results are rolling in like this short summary from the National Institute of Health:
My translation to English:
1. "Westernized diets tend to cause dysbiosis in gut microflora" ==> sounds like they share the same theory as you.
2. In Japan these researchers control Crohn's with a vegetarian diet where they allow fish once a week and meat once every two weeks. The recurrence rate of their patients is 0% the first year and 8% the second. No explanation why some patients have flare-ups the second year but I wonder if they get more lax with their diets.
3. I haven't heard of any other treatment protocol with this level of effectiveness.