If it were me I would get myself another opinion in the gastro dept. You might consider the Mayo Clinic or a large teaching hospital. These places have excellent drs. You say you have tried all the different medications. Does this include say Remicade or Humira. With as much medication that there is available for crohns surely there is something out there for you besides Prednisone. Wonderful for crohns but with horrible side effects not to mention problems associated with long term use.
As for the pain mediction its really difficult to say what may relieve your pain. Our bodies metabolize medications so differently that what may help me will not even touch your pain. Do you see where I am coming from with this. I have CD and I am a chronic pain patient. If you have not tried Lomotil for the diarhrea give it a shot, its by script only. Most of the time codeine based pain meds also will help slow that problem down.
Good luck, Susie