100mg minocycline 1 time a day is starting not to work for acne anymore after 3 years, would upping the dose possibly help? Any other options?

Probably no. The P. acnes bacterias has probably become resistant. 3 years is a very long time to be taking Minocycline. It has too many side effects, with long term treatment may cause autoimmune reactions (systemic lupus erythematosus, autoimmune hepatitis). Other alternatives are topical antibiotics like Epiduo, Benzaclin, (clindamycin and benzoyl peroxide) etc, laser treatments can be very effective.