@jozer
You managed to encompass pretty much everything I have experienced and it appears many others have as well based on what I’ve read on this forum. So much confusion…you almost laid out what should be basic testing protocols…have you ever tried lactaid instead with calcium. I had a problem for several years that required I see a specialist…it took a few but I finally got a great one. No anything with “…ose”
No lactose, fructose, etc. after two years plus of horrible intestinal pain (ie like molten glass going through) I was better within a couple weeks! He wrote a book and now many gastrointestinal docs are or should be aware of the “fodmap” diet.