Car lost all electrical while driving

You shouldn't be able to wiggle either one. If the attaching stud is loose on the starter is loose, then it sure won't have the contact acrea to carry the 200 amps needed.
That’s what I thought too. But...

Got under the hood last night. Cleaned up battery ground to engine block and battery terminals (pretty new/clean so not much there). Then got under the car - starter stud was loose and the attaching nut was also loose, and lots of gunk on the connectors. Cleaned them all up and tightened the stud back up, and did the same to the smaller stud and wire (to coil i’m Pretty sure). That seems to have fixed my loss of power on ignition problem. But...

During test drive, voltmeter gauge was pulsing, same for gauge lights (tach anyway) and speakers going on and off intermittently. So today I changed the voltage regulator (labeled Relay on the Duralast box - I think it’s the same thing) and that fixed the pulsing problem.

So in sum, my lost power fix was at the starter studs and the connections there. Seems like once everything tightened up it was sending too much voltage for the old regulator to handle so a new one saved the day. Hope that makes sense and helps out anyone else who encounters this problem!