I've taken at least a trillion CFU a day, with no lasting effect. Though, the first time I took probiotics, my digestive system started acting normal. My poop became a perfect type 3 and I was going every day, with incredible urgency without the need for laxatives. (Note, my stools have mostly been type 1, rarely type 2, all my life). And for the first time in my life I was gaining weight without even changing any part of my diet. I was gaining a pound a day. However, that effect ended in a week when I changed probiotic formula. Returning to the previous formula did nothing. I lost all the weight I gained. Whether or not it would have lasted without changing formulas, I'll never know. If it would have stuck, I would have probably been healed. The only thing it consistently does for me now is increase stool frequency. Even among the home-made kefir groups, once they stop consuming kefir, many of them return to how they were, and they have to let it ferment for days to achieve several trillion CFU per serving.
When no one is willing to help you find a stool donor or become your stool donor, you're left with experimenting with everything else. Being in that boat, I've tried just about everything else, and all it does is somewhat help manage my symptoms. And it's expensive to keep it up. But all of this have simply proven to me that an FMT is all that will fix me. Yes, there's a chance that the FMT could make me worse. But without an FMT, I have a 100% chance of death. 50% chance of death is always better than 100%. No point in being scared of death with odds like that. Yet, the knowledge gained is stuff you won't ever find anywhere else. Though, it's kind of fun watching a new study come out confirming what you already knew. Too bad they take forever to confirm it, and the general public could care less.