I too morphed into Crohn's, about 15 years into my '92 jpouch. I'm 62 YO. Fistulas, abscesses, etc. I tried a lot of homeopathic supplements, diets (sorta), etc., but nothing made a difference. Had 2 setons, still had pain, accidents - it was a real struggle. My surgeon (Cleveland Clinic) did not recommend fistula surgeries, her experience was that most fistula surgeries fail. I was not interested in biologics, as I did not consider them a long-term solution; indeed, none of my doctors encouraged them.
Finally, had the pouch diverted in 11/17, about a month prior to the planned removal, due to large abscess and wrap-around fistula. A year later, I had the pouch removed and bottom closed up. The thought was that the "Crohn's" was limited to the pouch/cuff. So far, so good, no new fistulas or abscesses, knock on wood. The stoma is working well, and life is definitely better than it was with the fistulas. I'm not pushing removal by any means, but in my case, it was a matter of now or later and as it turned out, I waited too long, but am pleased with my health at this point in time.
I hope you find your answers - please discuss further with your doctors.