Saffy, sorry you are going through hell right now. I really don’t have any suggestions for you other than to share my own experiences. I know they won’t be a great help, but here it goes.
I think I may have blamed fat a little prematurely. I have been doing lots of experimenting with my diet and I think the problem for me was really the BONE BROTH! I was listening to a talk by Dr. Siebecker on SIBO and she mentioned there are GAGs in the cartilage around the meat and bones and the GAGs can be consumed by the bacteria. The bacteria then produces gas and voila heartburn.
So now I cut out all the fruit and I am slowly ramping up the meat, but I avoid cartilage and really any meat around the bones.
I still wonder if there is not something to the deconjugated bile by SIBO. When I was eating lots of fruit, low fat meat and lots of non starchy veggies I had a lot of heartburn. I am sure the fruit fed the SIBO. I also tried just fruit and lettuce for a day and was in total hell by the end of it. Could the combo of well fed SIBO and some fatty meat, which causes lots of bile to be released be a double whammy for the SIBO? This idea would coincide with the trouble I have eating bone broth with the meat. It seems worse for sure. Although, it could also be that there is still a lot of cartilage in that meat because it came directly off the bone and so it is just a double dose of GAGs.
Does the heartburn calm down for you at all? For me it was not too bad in the morning and it would get worse as the day went by depending on what I ate. I did try fasting and I would get heartburn by the afternoon even if I ate nothing, but I guess that could have been the deconjugation of bile by the SIBO.
Could you try some chicken breast and well cooked spinach or lettuce? Check out Dr. Siebecker’s site. One of the treatments is the elemental diet. I have never tried that, but maybe you could go that route and let the SIBO die off.