Dishwasher Drain Pump: How to Test?
I have the same problem you had.  I am not sure of the proper impedance you should have.  One internet repair place says 200 ohms for a good motor.  I did the same thing you did (same problem - dishwasher not draining) lines were clear to disposal - I also exercised the check valve which is in the 90 degree black elbow right off the drain pump on my machine (Whirlpool model WDF760SADM) forward and backward to ensure it flowed and would stop flow in the reverse direction, which it did.  I do not have leads that are compatible with the motor to check that it runs.  I am going to replace the drain pump to see if that is the problem.  Also, the jerky motion on the impeller is due to the magnetism on the motor.