I fall back to bone broth cooked for 24 hours to get all the gelatin. If I do not have this then I buy organic gelatin and have it with very simple foods. Perhaps you might try gelatin with diluted grape juice.
If the bone broth is ok on your guts then you might add some very well cooked carrots and some plain baked meat. You can pureee this, add a bit of herbs, and you will have a savory smoothy. Very simple and healing foods for those folks that can take it.
I would eat small meals as often as I can stand it. Can you take fats, like avacado, maybe yogurt made with 1/2 and 1/2 (high calorie and low lactose).
Have you tried activated charcoal?
I could not take high doses of pentasa either, but I was lucky as I am able to get by with a low dose. I was also lucky as pred was making me crazy but entocort had virtually no side efects for me.
I know this is not an answer to your question but just trying to throw some suggestions your way