You should uninstall ws2812 and probably stop the daemon also, since neither of these are needed for UnicornHAT to work and the daemon might well be interfering by writing out blank frames to the hardware even if you're not talking to it.
Unicorn HAT can be driven brighter in some instances, but the brightness cap is there to protect it from the worst possible scenario which is all pixels driven full-white at 100% brightness. In this case it draws not only more power than you could reasonably ever supply to a Pi without modification, but also too much for the soft-start circuitry on UnicornHAT to handle ( which is there to protect the Pi ).
Thanks for the heads up regarding the indent blunder, I've fixed it and pushed 2.0.6. D'oh!