["QUICK-SILVER"]

A 12 volt test light is all you need to diagnose this.
Lets start at the fuse box: Tail light fuse also powers dash lights. Power comes from the tail light fuse to the headlight switch. When the headlight switch is pulled on, dash light power goes through the rheostat, behind the knob, then back to the small inst fuse in the fuse box. Then the gray wires come from the small fuse to the instrument lighting.
So dash lights have two fuses in the fuse box, one before the headlight switch and one after.
All the gray wires are dash lights. The one that went up the steering column, would've been for shift indicator on cars with column shift automatics. Or possibly lighted key on 69 up models.

So with your test light check both ends of the tail light fuse for power. Turn lights on and check both ends of the little instrument light fuse for power. If it's working up to there, hold the test light on the small fuse and twist the headlight knob. The test light should bright and dim like the dash lights. From there move to gray wires and instrument light bulbs checking for power with your test light.
Only the dash lights in the instrument cluster use the printed circuit for power supply and ground. Heater controls, the wire that goes up the column (shift indicator), etc., aren't affected by the printed circuit.

If you lose power anyplace while testing, check the last components power came through. The headlight switch can work and rheostat spring be broke, rusty, corroded, and the dash lights won't work.

You can use a jumper wire from the tail light fuse to the instrument light fuse to by-pass the headlght switch if it's suspect.

Check it out again and post back. Don't buy parts till you need them. everything can be tested before replacing.

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"If this is supposed to go to the column, how do I yank the connector off the column to hook up the errant gray wire?"
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Each wire terminal in the plastic connector has a tab that you can release with a pic (paper clip) and slide the terminal out of the plastic connector. Then you can pull the turn signal switch and the wires will slide up and out of the column. Tie a stout string on the wires before you pull them out. It makes pulling new ones back down alot easier.

I don't think this is anthing you need to worry about with the dash light problem. Maybe somtime else, just not now.