ESC scheme ADC problem
First of all, you should be looking at the voltage difference between ADC-x and ADC_Center, either by using two channels in differential mode or connecting scope ground to ADC_CENTER (with ESC power supply isolated from scope ground). ADC_CENTER is the 'virtual center point', equivalent to the center tap voltage in a star-wound motor.

If your wiring is correct and you are applying normal 6 step commutation then at every step one phase should be high, one low, and the third at ~1/2VCC with back-emf riding on it (sloping lines in the graph below). Therefore if you compare any two phases they must be out of phase (by 120&deg; if the commutation timing is is even).

In any case, the only phase you are interested in is the one which is currently floating. If the ESC is in sync with the motor then the Zero Crossing Point (relative to ADC_Center) should be approximately half way through the commutation step. If it's not in sync then the ZCP will be random, but the motor probably won't be spinning either (since the coils aren't being activated with the correct timing to keep it going).