Firecracker, a lot of people with Crohn's disease take MTX so I don't know why your GI was so upset. Especially when you said you have had an allergic reaction and/or intolerable side effects from other meds. If you can take one med that works for both, to me that would be a good thing. Just be sure to get regular bloodwork done and take folic acid.
Just a note, my cousin (who is a doctor and has Crohn's) takes MTX for his joint pain. Says he could not function without it. I am sure I have read that others with arthritis are taking MTX as well.
Good luck in your search for a new GI and hoping this works for you.