the extra current consumed is probably because the breadboard. at 1.2Mhz every node starts to oscillate. board layout plays a very important role in switching converters efficiency. I have learned this in a very hard way when designing buck-boost converter with lm5175, all my traces were fat and short but the board didnt work because of the bad layout.
That's some nice driver - could be perfect for a bike tail light with a supercap to keep it lit during short stops, and possibly supporting different working modes (brighter, darker, blinking etc.).