See the last page here:
https://cpb-us-w2.wpmucdn.com/...ke-Down-Recovery.pdf
What kind of a doctor do you have? Is this a GI or a surgeon? Anal sex is usually not recommended, and in this document it says “prohibited”.
Your fiancé does not sound like a person who would stick around if you were to go back to an ileostomy. No possibility of anal sex with a Barbie Butt. This sounds like a great test for finding a good husband. If he dumps you because you don’t want to have anal sex with him -with a j-pouch!!- then it is great news! You won’t spend your years or even decades with a person that is not right for you. Many people with colons are not interested in anal sex, and the same husband-fitness-test also applies to them. But in your case, it is a test that you cannot waive. Your future husband has to pass that test, and your fiancé fails it. If I were you, I would dump him even for wanting to try it.