sudden loss of all electrical power?!?!?!?

I explained it to you here:

 

I am trying to make sense of that- by “from battery to ground”, it is meant to connect one end of the jumper cable negative lead to the battery negative lead, and the other to the vehicle frame? Is that right?

“battery to starter solenoid side (not the starter side)”? I see only 2 connections on the starter- one is bolted on, the other with a plastic quick connect. Is it intended that the positive jumper lead be connected to the battery positive terminal, the other end to the starter bolt electrical connection? I don’t get this solenoid side vs starter side distinction- at all.

 

The battery positive cable is bolted to the starter. There is another short thick wire coming out of the starter that goes to the actual motor. In between these is the plunger (inside) that the solenoid pulls in and makes the connection between these. If you hook the power directly to the motor side it would start turning even without the key turned to start.

You would want to jump directly to where the thick cable from the battery is bolted then turn the key to start.

This is all a bit risky because if the jumper cable accidentally touches any part of the starter you will get a big short and lots of sparks, etc. And the vibration of the starter turning could easily wiggle the jumper loose and cause it to short.

 

I recently redid my battery terminal connections as well die to the dame exact problem you described. Now my volt meter is showing 14.3 charging and 12.7 with everything off.