David:
I admit to little experience with folliculitis decalvans. What I do know is that controlling it is extremely difficult. All the medications you mention are recommended for at least a trial. It sounds as though you have consulted physicians of considerable sophistication. Have they done scalp biopsies? Are they certain of th diagnosis? (Scarring conditions of the scalp are notoriously confusing.) If they are aure of the diagnosis, and they may well be, then it sounds as though you are getting rpoper care, and need to to learn by trial and experience along with your doctors what works and what doesn't.
Cure may not be possible, but control should be a reasonable goal.
Best.
Dr. R