1. "Does the "field" connection on their alternator allow its output to be turned OFF remotely?"
  2. "If so, is it connected to the alternator's actual field winding, or is it an ON/OFF control signal to the regulator?"


I have no idea. Did some fishing around and the consensus is that the Nippondenso alternators field goes to the windings but until you know for certain, you don't really know.
Guess I'll just have to check it out after startup! Will post a reply when I have the results.

Agreed about the ammeter. I'll use the G3x to monitor its output.

Thanks for the insight, Eric!