Well, just because the medications like 6MP, Imuran didn't work before, doesn't mean they won't be a good option for maintenance. Sometimes, the disease is just too far along for the meds to work, but they could work for preventing future flares. 6MP never worked for me while I was in a full flare, at least not unless I was also on Remicade, but I'm back on it for maintenance. I would not take Remicade for maintenance, but I've had serum sickness to it.
As far as the TPN, it wouldn't hurt to bring it up with your doctor. I know they try to stay away from it these days because of potential liver problems with long term use, but you would only need it for a short time to get your weight up to a safe level for surgry.
49 years old, Crohn's Disease
Six resection surgeries, permanent ostomy, adverse reactions to Remicade, back on 6MP for maintenance, hoping for a long remission from this last surgery.