Ammeter bypass turning over alternator

Chrysler ECU doesn't draw a lot of current. Based on your test, how it is tapped in isn't effecting the voltage drop in the line. So doesn't impact the analysis.
Radio hooked up but if its off shouldn't add load.
If its its a solid state regulator, then its probably no good.
Confirm that.
1. Slow charge battery using a charger.
2. Have a way to jumper the regulator with a short wire (connect the J2A to the R3)
Start the car and get it to slow idle.
Connect the J2A to the R3.
The ammeter should show charging and the alternator's output should be found through all the feeds.

With the regulator bypassed, the rotor is producing it's maximum electromagnetic field without a break. System voltage will increase with rpm. So make the test, don't rev the engine, and disconnect.

Before doing that, I would hunt down why the alternator's batt terminal is not showing battery voltage. You can do that with the key off. Heck you you can do that with the battery disconnected. Do a continuity and a resistance test.