I've already ordered some benfotiamine.

Carbonate ions (an alkaline buffer) are different to dissolved CO² (acidic). The carbonate does react with acid to form CO² though.

I nearly lost consciousness when I filled a paper bag with concentrated CO² & breathed it in. My field of vision shrunk & I felt slightly high. That was when I stopped playing with my CO² levels beyond conscious & deliberate breathing.

I'm keen to understand how benfotiamine is so important to you but I think I'll just have to wait until it arrives.