Can't believe how helpful everyone is even on July 4th. I wish I could buy you all a burger and a beer.
I just did what Joe K suggested: "try the jumper cable between the battery post and the "knob" underneath the starter switch (remove the two screws and take off the starter switch.)"
Tapping the knob with the cable produced a medium spark but when I held it on for a sec, the starter turned! So it appears to be working.
Re the starter switch, using a voltmeter there doesn't appear to be a short. I get no continuity between any part of the casing or rod and the copper flap. They seem to be correctly electrically isolated. See pic.
But if the starter turned, it seems to imply the switch. But it's pretty simple. I don't know what could be actually wrong with it.