Try Genestra Brand HMF NUERO probiotic powder..derived from a human strain. Included in this formula is l-glutamine (good for sealing leaky gut) and let me tell you I've tried almost everything but this is the only thing that works wonders for me. I'm like you, intolerant to gluten and mercury issues from Amalgams but I had those removed last year. Didn't noticed a great improvement after removing them...Never got tested for the mercury but maybe you should look into it? I just go by symptoms and when I feel my gut balance out alongside detox symptoms, I know I'm doing the right things. Right now I'm doing nothing too crazy except for a low-sugar diet, gluten-free, and this particular probiotic. That is all and the improvement is remarkable.
They recommend 2 doses per day but I only do 1 dose every couple days. I wait for each dose to work it's magic because die-off symptoms were a bit much. If you're anything like me you will notice a change after the first dose. Ride it out and sense what's going on after each dose. Don't overburden your body with die-off..Take it slow. Don't underestimate a 1/4 teaspon of this stuff.