6-weeks post-takedown, it could be recurrence of the stricture. However, since you are so early in the healing / recovery process, and you can verify the opening is still index finger-wide, it could simply be your pouch healing up and re-adjusting to things. Pouchitis can cause difficulties emptying as well, and it is not uncommon to have symptoms 6-weeks post takedown (however, most surgeons will not consider treating it as such at this early point after takedown).
My advice: continue self-dilation, and see if you can't adjust your gut flora with some good yogurts or probiotics to see if that helps. I think your surgeon is optimistic if he thinks metamucil will bulk your stool enough to stretch the anastomosis. Even when I have formed stool, I don't think it would have the ability to stretch anastomosis tissue.