UPDATE: Working treatment - after 10 years of non-stop suffering!
I discovered by complete accident that when I take an over-the-counter antihistamine, fexofenadine (generic Allegra), my intense bloating symptoms decreased dramatically. They are not eliminated, but they are 70-80% reduced, and I can bend over to pick things up and can go up a flight of steps without severe chest pain.
None of the GI specialists I have visited over the past 10 years mentioned this as a treatment option, but there are several academic papers on pub med that discuss this, so it's definitely an up and coming topic.
I am now going to add an additional non-drowsy antihistamine (loratadine) to the fexofenadine to see if it works even better.
Since none of the many antibiotics that I have tried really had this dramatic of a positive effect, I would definitely give the anti-histmaine OTC drugs a try, since they are cheap and very safe.
UPDATE May, 2019: I have added H2 blocker antihistamines Tagamet (Cimetidine) and Pepcid (famotidine) to my regimen, and these have substantially cut down on my bloating. (Both are available as cheap generics.)
I take generic fexofenadine with a glass of water first thing in the morning. I take the tagamet a few hours before eating dinner and take the pepcid immediately after eating. They do not eliminate the bloating, but definitely seem to suppress it.