Fuel gauge scramble

[Green Machine 79]

1979 c20 pickup

Fuel gauge has only worked a few minutes in the last 4 years. Now that i've gotten everything running smooth and perty, my wife wants this detail taken care of.. It's been stuck on high.

I should know better but i assumed maybe it'd be an easy fix. I lowered the tank to find the sending unit destroyed by rust and the lines rotted to the point they came right off rather than surrendering the hoses. So i replaced the sending unit and hoses, but no change to the gauge.

Following the wire from the tank it seems to cross over to the drivers side before moving forward. There is another wire that comes from the same tube but runs up the passenger side and goes up by the starter.. I dont see any issues along the paths. Its appears well protected all the way.

Next i went behind the gauge cluster and found a brown w white stripe wire had been folded back on itself at some point and appears to have melted itself along with hardening its neighbors. I figured on soldering those few wires but after looking over the guides, the dark blue and light blue wires are still functioning fine.

I still have not been able to figure out why my temp gauge is also not functioning but figure it's probably related..

So yesterday i decided to try and test the gauge itself. I was getting a 12 volt reading from all the gauges ports (with gauges removed). Then i tried to ground the fuel gauge (inserted back in port) with a jump wire. I heard a tick and now my fuel gauge needle is not moving at all! When i test now i only get around 6 volts in the empty port.. I don't understand how I've cut the voltage in half??

The circuit on the gauge cluster looks ok. It's a bit green in spots but no brakes along the way.

Everything else on the dash works great. No trouble with lights or turn signals or anything else.

Should i just run a new wire up from the sending unit? Is it a direct connection?
Any help would be appreciated. I'm lost on it. And i feel like i need to take a class just to be able to make the diagrams useful

Not sure if these pics help but i got em..