You should forget the external regulator plug and run the red wire from it directly to the no,2 on the alternator and run the brown wire next to it directly to the no. 1 terminal on the alternator.
If you unplug the alternator plug and measure the volts on the white wire (no. 1) you should get zero volts key off and 12 volts key on.
The brown wire at the regulator plug is where you should get 12 volts key on and zero key off. Then it is jumpered to the alternator no.1 via the white wire in the regulator plug
to the no.1 at the alternator plug (white wire).
The red wire is 12 volts constant at the regulator plug and at the alternator plug no.2
via the blue/red wire.
The reason you got 8.2 was because you measured it plugged in and there is a 10 ohm resistance in the brown/white wire from the key switch. So your readings are where they should be.
That appears to be one of those jumpers for the regulator plug and it seems to be working, so you might as well keep it.
Here is what it does.
here is how I do it.
