It looks like most of your efforts have been aimed at your scalp.

When I get conditions that don't get fixed by surface treatments, I have to go back up the metabolic chain. What can I do to affect the cells before they become dandruff (in this case; dandruff has not been my problem).

My intermittent acne clears up because of changes in my diet more than any topical treatment I have tried. Ditto weak fingernails.