Given your history, the imuran and humira combination sounds appropriate. Everyone is a bit worried when starting new classes of UC medications, myself included. What helped me greatly was looking at the actual risks versus benefits of those medications. The benefits far outweigh the risks.
I found the following risk versus benefits presentations to be helpful from the Crohn's and Colitis Foundation of America:
Webcast:
programs.rmei.com/CCFA139VL/presentation/player.htmlTranscript
: http://www.ccfa.org/assets/pdfs/risk-and-benefits-transcript
.pdf
I've been on remicade (a sister medication of humira) and 6mp (a sister medication to imuran) since 2012 and have yet to experience a side effect from them. I did experience a remission though! It's been a much quality of life since starting them with infrequent and mild flares (better than the 20+ bms I had before taking them). Imuran actually metabolizes within the body into 6MP, I save a step.
You've tried about
everything you can (from naturals, to diets, to mesalamines) I'd say humira and imuran are a wise next step!