Excess current in Ignition 1 circuit?

Again, I appreciate everyone's input.

I've removed the terminals of that circuit from the connector to isolate them. Until I can dig deeper and test further I'm going to physically monitor that connection for heat. I imagine some heat would be normal but it was getting scary hot before. I've seen what heat/current damaged wiring looks like but overall the insulation looks okay.

I would also not be surprised if the terminals in the aftermarket ignition switch were not made to the same standards they were in 1970. If they're just a little bit looser....