Hi Owww - you sure are dealing with a helluva lot! I'm really sorry the colonoscopy messed up your fissure and that it found colitis.
I have not read any case on this forum where someone had a colostomy bag, but I do believe there was one fellow, Lars, who was seriously considering it. Unfortunately, I don't think there were any updates after he reported that he was discussing that option with his doctors. Is this an option that you can raise with your doctors? I can definitely understand why you would want to do that. I think a few of us here wished we could get a colostomy bag until we got healed, even without Crohns to deal with!
I really hope the Endocort works, but without making your BMs too hard. Unfortunately, in my experience, diarrhea can irritate fissures too
I wonder if you would be able to take Miralax if the Endocort causes problems?
I really hope your doctors can give you some options. Living with a fissure is truly the hardest thing I've ever had to endure. You definitely have my heartfelt sympathy and I really hope you find some relief soon.