During the cars in service life, the horn ring stopped working, and someone at the fire department put a push button on the dash. Because of the way that it was installed, told me that it wasn't done by someone familiar with automotive wiring. I took the column apart starting at the top, and when I was done, I had the entire column out of the car and found the problem, and Chrysler made a mid year change and replaced the spring copper strap with a piece of 12 gauge wire and a couple of screws. I learned about this from the parts car that I had at my disposal. Unfortunately I wasn't able to make the upgrade without changing both the steering gear box and the column since the change required drilling into hardened steel, so I did the next best thing. I used 2 small worm gear clamps to clamp the spring copper strap back to the steering column, and got it working correctly. I don't remember how much wiring I had to fix to remove their Rube Goldberg way of getting the horn to blow, but when I was done, I had a small pile of wire left over. There were a bunch of other problems with the wiring that I had to repair, for fear that if I didn't, the car might go up in smoke. A lot of the wiring done by Pinner needed correcting.
As for the dome lights, they are all hot all the time at the bulb, and when you open the door the switch makes the connection to ground and the bulbs illuminate. The switches do not ground out the hot wire as you said above, because if they did you would have a massive short circuit on your hands. If the drives door doesn't activate the dome lights, check to see if the white grounding wire has fallen off of the switch.
Moving onto the single wire that goes across the floor of the rear compartment, if you connect both of the cut ends together, you will disable the other switches and the interior lights will stay illuminated. I spent hours trying to find where that wire is damaged causing it to ground out, but I couldn't find it without taking the entire rear compartment apart, and even then, there was no guarantee that the fault could be found. As a result, I just left it taped up just the way that I found it. I believe that it was that way when the car was delivered, and even the Pinner factory wasn't able to find the fault. Sometimes some issues can't be resolved unless you start from the beginning and work your way back. Unfortunately, there is no wiring schematic that shows where the wires originate from and there they terminate. Automotive wiring isn't as straight forward as many people think it is, and a lot of junctions are created along the length of the wires, by cutting, splicing, and taping the connections. The worse part of trying to repair these problems is that you have no idea of what was done along the way during the cars lifetime. Fixing the horn blowing problem took me the better part of 2 days to sort it out, and I had the luxury of having a 1963 Chrysler New Yorker at a local salvage yard that I could pick for repair parts.