Most of the treatments for prolapsed Pouches do not focus so much on diet as they do on muscular therapy. The various types of prolapsed pouches and the treatments for them are discussed in this article. Protein diets is not one of the treatments I read about here and I am curious as to what the theory behind it is. I would read this, a co-author of which is the legendary Bo Shen:
If you are near New York City, I would suggest seeing Shen and getting a second opinion, because you are suffering through a diet that does not appear to be on the radar of Shen approved treatments.