You have hit all the easy stuff and gave great details of what you have done.

A digital volt meter can read stray voltage that goes away once a load is applied so the readings just show that the wire isn't broken.

Do you have a wiring diagram?.

Did you apply power to the clutch to check engagement? When selecting clutch wires, be aware the compressor probably has a RPM sensor that detects clutch slip so applying 12V there would damage the sensor.