Since I have no personal experience with inflamed post-surgical sites, I would just be guessing. So I would agree with your doc and just give the Stelara good long trial and see how it goes.
As for the Entyvio, I know that the protein that Entivio binds to is more heavily expressed in the large bowel than in the small, but what that says about the rectum I'm not sure. Extrapolating from the large bowel, it might be reasonable to theorize that Entyvio would work better on inflammation in a rectal stump than it would on some portion of the small bowel., but how that compares to what Stelara would or wouldn't do, I have no idea.