Very good questions. I will just pass along that my chiropractor/acupuncturist/vet strongly recommended SmartGut Ultra last year when my mare was reactive to her “stomach points” (acupuncture speak)–it had great results in scientific studies which she had been reading. I had noticed my mare’s sensitivity when grooming her (it was a noticeable change). After using SmartGut Ultra for a month, my mare was back to normal. I kept her on SmartGut Ultra two-three months and then downgraded to SmartGut. If she has any flare ups, I plan to go back to SmartGut Ultra.
You may want to try the Ultra. It has higher magnesium as well additional ingredients for ulcers. It is more expensive than SmartGut, but you probably would not need the Mag 5000.
You may also want to consider using just the SmartGut or SmartGut Ultra and a B vitamin supplement.