I use Imuran along with the biologic Entyvio. Sometimes it takes more than one medicine combination to give you the best "normal" for you. I understand your frustration with all the issues you've had to deal with in the past, but remember that each of us is different and Humira might work out just fine. If it doesn't there are still others to try before thinking about pouch failure. I did the Humira for a while, but it didn't help me. Switched to Remicade, which gave me a reaction, and am now on Entyvio. So far things are going well - much better than before I tried any of these meds. I know it is no guarantee things will work for you, but don't be afraid to try something else to get the relief you need.
With the high cost of biologics, I'm not surprised that the insurance company is stalling paying for the treatment. Thankfully there a people in the GI office to help fight through all the hoops to get you (and me) approved. I
Thinking of you while you keep fighting!