Another thought: Have you tried taking digestive enzymes? Those usually include the enzymes to digest fructose, so if you are having fructose intolerance issues, enzymes should help. Digestive enzymes were life-changing to me, so I am a big fan. Unless you are sensitive to a component that they are made from, they are very safe to try. The kind I take is called "Enzymedica Digest Gold." From what you have said, this sounds like it could potentially be a really good match to the problems you've been having.

Probiotics can help too. I would say that taking digestive enzymes solved about 85% of my problems, and probiotics were the other 15%.