I haven't read the above in detail. It's been some time since I looked at Chris Armstrong's research. At one stage he was looking at low gut pH (acidity closer to neutral than it should be). He demonstrated high levels of volatile fatty acids in your blood which indicated that food was being processed lower down in the digestive tract. Interestingly he proposed that once you had this problem then you were stuck with it (negative feedback loop). Lower gut acidity leads to lower stomach acid production, which leads to altered metabolism, which results in lower acid production. He did a webinar possibly December 2016 and published a number of papers all readily available (and reviewed on Cort Johnson I guess).
I kinda did an experiment on myself pertaining to this decreased acidity as well. I noticed that my symptoms worsened substantially when I drank water with bicarb or added electrolytes which are mostly alkaline. I mean I get vertigo and decreased fat absorption ect. I started eating an apple without most of the skin besides one strip prior to breakfast every morning and when I felt off at night and it has decreased some symptoms as well as increased my ability to digest nutrients in the proper area! I also have been having a drop of oregano oil every night with some homemade soap broth which has helped decrease SIBO symptoms and keep the gut balanced. I have not had much anxiety or mild depression after eating like I have had.