[papajam]

Your description, "Power at the battery is 13.2v. Power at the starter (and at the alternator cable terminal board) is 0 to 10v,....." tells me that the problem is in the positive battery cable to the starter assuming, of course, that the chassis ground strap between the body and the right side of the transmission is OK.
Try checking the voltage at the starter with the negative voltmeter lead grounded at the battery. If you read battery volts, the chassis ground is the problem. If the reading is less than battery volts, the positve cable or connections are the problem.