Have you tried anything that might allow you to eat a wider range of foods, such as Metamucil?
Also, with the foods you listed as your mainstays, are you vegetarian? The reason I ask is that lowering carbohydrate and increasing protein can be a good strategy (obviously depending on your doctor’s advice). But increasing protein can be take a bit of thought for vegetarian j-pouchers that have to avoid legumes.
I eat a wider range of foods than you, although still avoiding high insoluble fiber foods, and have been trying to lower my carbohydrate intake for another reason (not diabetes). It isn’t easy, plus I am vegetarian. I even tried to go back to eating meat and fish, but just couldn’t do it.
You can see my recent thread about acarbose. If you are prescribed that, do start slowly and cautiously, ditto with any medication that has diarrhoea as a possible side effect.