If the VR failed open and the alternator was allowed to overcharge 15+V, that would show up as a constant charge on the ammeter. Obviously if it failed closed and kept the alternator from charging enough (below 12.5V), the ammeter would show a constant discharge most likely.

Yeah voltage can drop and you can have lots of current, in the wrong direction (from the battery). Either way the ammeter tells me this.

BTW I had the cable custom made so it's not spliced together to achieve the 6" extension. The leads are 4/10 ga if I had to guess...whatever the factory used. Cables aren't corroded and grounds are fine. The starter grounds to the block I would assume and I have a 4ga neg cable that goes to one of the A/C compressor brackets on the WP housing. It's aluminum, not painted, and free of corrosion.