Understanding ignition wiring on my 1970 Dart

None of the other wiring matters unless it is shorting to ground, which should cause smoke and "meltage." Again, check at each point AND THE SPLICES for loss of power. "Wiggle test"

Your main places of failure are (in no order)

the ignition switch itself
the ignition switch column connector
the bulkhead connector
the two splices, rarely
nice job. couldn't have said it better. honestly, probably couldn't have said it at all, without a lot of research and head scratching, hahaha.