Hey, Max. My disease presents like yours. I operate as if I have CD, but none of the 3 GIs I've been to have been willing to give my IBD a name. Nonetheless, I did much better on Pentasa than on Asacol.
The side effects from Pentasa finally got me to quit using it, but only after I'd taken it for about
6 years. It can cause tinnitus, which I already struggle with because I live in the subtropics and my allergies are awful. I replaced Pentasa with balsalazide and so far, so good. My scope was last week, too, and I had no visible inflammation anywhere, including the TI and cecum and rectum. I get biopsy results on Friday.
I don't think the contest of who's IBD is the worst is how anyone should spend their time. YOUR IBD is what you have, and you need to figure out how to best manage it.
Oh, and the next step to treating your TI is probably not imuran but entocort, although you can't take that for more than a few months. Since the involvement of the TI seems to be mild, I'd hope that Pentasa can take care of all of it.