Experimental feedback scheme in DC-DC boost converter
I'd suggest what you are trying to do would work with the changes shown below.

The boost convertor would threshold the Vce of Q2 at about 1.5V.
D2 ensures you can't swing FB beyond supply.
C2 is for ripple reduction on Q2 collector.
C1 is for storage for the boosted supply.   

I'm not sure about operating this at over 1MHz, but it should work at 600kHz.     

I also assume you want to run multiple strings of LEDs from the same boosted supply (it's actually quite clever). 







simulate this circuit &ndash; Schematic created using CircuitLab