That is a LOT. To reiterate, if your VR is correctly regulating at 14V (nominal) the "let's say" 1.5V you read will ADD to that, causing the battery to be charging at 15.5V. Also, this reading is not usually stable, meaning it can get worse, or better, as the bad connection changes
Now you need to go "back" through the various points in the system.......the bulkead terminals, the ignition switch connector ......and see where the drop is
So extend you test leads so you can leave one clipped to battery +. With the key in "run" as before, check the voltage at the ignition switch connector, both power coming to the switch and the blue IGN 1 going out. If it is already dropped some at the switch feed, then the problem is "between" the switch and the battery........namely the bulkhead connector
One way around this is to electrically cut the blue "run" wire coming out of the bulkhead. Us the bulkhead side wire to trigger a relay, and feed the other end (engine bay side) of the wire from the load contact of the relay
