Sadly, fish TB isn't curable. It's not equivalent to human (lung) Tb. Mycobacteria are a special kind of bacteria -- their outer cell layer is very resistant to many types of antibiotic and sterilization methods. Kana and B6, imo, would not work.

I really don't think that TB should be a big worry here. As you said, the fish only has presented this curved spine since being ill (which points more to the active illness as a cause, rather than another infection, TB). As well, you're not seeing any ulcerative lsions, nor wasting (rapid loss of weight).

~Ash