Stall at 55: Did it cough and sputter or just died out? Stall at stop: Dont think this is electrical, but carb tuning, especially as you keep it going with a throttle blip. Another thought occurred to me, make sure your engine breather is free and clear. This is the tube that comes from the crank case (black, about 1/2 in diameter) and goes to the catch can by the battery. Engine needs to breath but i dont think it'll cause a stall at 55... ive been wrong before tho.
...Could the clogged breather cause the faltering coming to a stop?
I don't think so. Have you turned the carb yet when the bike is nice and warm? Did turning up the idle make a difference?
Compression test...warm, full throttle 158psi.