First time poster, long time reader.

I’ve searched and searched, and got almost all of the info I needed, but I’m still stuck.

2000 F350 DRW 7.3L

Driving to Home Depot past dark the other night and I notice my instrument lights (dash) are not working. I look in my rear view mirror and notice my fender marker lights are out to. I pull over and non of my running lights are working. Quickly I check brakes, OK, reverse light, OK. Low beam and high beam OK, left and right turn signal OK. Hazard lights OK. Literally just runners. So I find the fuse in the engine and it’s out. So I replace. And it pops again. It’s -25c (-13F) so I decide to just get to Home Depot then home with my hazard lights on. I read a ton of forums and check all the usual suspects. Nothing wrong. The next day I put a new fuse in and now only my front runners and eyebrow/clearance lights are working. Running boards back still are out, but not popping the fuse.
So today it’s a nice warm day so I get underneath and trace the wire harness running from front to back. Power on all wires and fuses are functioning. I get to the back of the truck and right above the spare tire the BROWN wire is off and floating around. Looks like it had been wearing on the frame. I tested it and it has 12v on it.
so I cleaned it up and reconnected it. As soon as I reconnected, it pops the fuse.
this is where I’m stumped. If it was just a cut wire, why would it pop if it’s no longer touching the frame? Would burnt bulbs cause a short that bad? All original lights. No LED.