You have to use the OR/BK wire instead of white when you test the baffle motor.
You do not need to measure the thermistors resistance. Instead just run the self diagnosis test (step 1 & 2). Also if the refrigerator thermistor fails, the control will cycle the baffle open for 10 minutes, closed for 10 minutes.
Most likely the problem is a bad air baffle.
- The part number for the air baffle is AP3084126
P.S. I'm afraid you did not read the service manual