Heath - My situation sounds very similar to yours - other then the fact that I'm a straight woman lol. I had UC as a young adult and eventually ended up with a total coloectomy and j-pouch. Knock on wood - I've had no big problems since my last surgery in 2001. I don't have any further association with doctors, except for my annual pap tests, and I pretty much live a normal life other than what I assume are typical j-pouch related symptoms such as frequent bathroom breaks, fatigue, etc.
Not to be overly graphic, but my husband and I have worked slowly (over the course of a year or so) into anal and find that it is a very enjoyable part of our sex life. He is very well endowed and we've definitely been careful about how deep he goes, but I just want to let you know that it has been possible for us.
I also relate in regard to insecurities about the appearance of piles, scars, etc. around the ass area and that whole "how in the world does he put his mouth on that!?" thought. Lol that's just something you'll have to deal with. Dim the lights and just try not to overthink it. If it doesn't bother your partner then try not to let it bother you.