Wow, that is an amazing account of trial and error, leading you to where you are. I hadn't heard from anyone who agreed with the big baby theory. I'm having a colonoscopy next week but my gastro doctor doesn't believe it will provide any constipation answers. My last one several years ago provided several polyps that were tied off so he's glad I came back in even if he doesn't have a solution for the problem at hand.
My constipation has evolved. I used to poop myself. Grateful I guess that doesn't happen anymore. It's perplexing that I go every 2-3 days and not very much. I'm the same weight I was and I don't know where it goes if it doesn't come out. The doctor didn't have an answer.
Anyway, if you find an answer, be sure to share it!