So how did Day Two go? It's lucky we headed home as I don't think there is any way, other than perhaps hot-wiring, that the Jeep would have started again.
Even with a wrench on the key, turning it (until it broke the plastic) would not let it start. We ended up spending 5 hours changing the switch on the column up under the dash, then adjusting the Park lockout mechanism--what a PITA!
One of the wires to the ignition switch (not key lock cylinder) had overheated and melted the "track" inside the switch that allows the various key positions to make contact. When it was forced to start at the campground, it also popped loose the shifter-Park lockout rod from the piece in the upper column that it attaches to (so it caught on the column shroud when trying to turn the key).
After that, we addressed the DS vibe issue. It looks like the yoke on the front diff may have been "sprung" as there was some play in the ujoints. We gently seated them tighter to one side of the yoke and the vibes stopped. I'm hoping changing the yoke does not require any re-setup of the pinion shims as it is necessary to remove the pinion bolt to change the yoke. It never ends, does it!?