Troubles with gas gauge, speedo fan, e brake

[WIDESIDE72]

I am having trouble getting the gas gauge speedo and fan working in my dad's 71 GMC.

The gas gauge read 1/4 way past full. I checked the sending unit wih an ohmeter and the meter moved when I moved the sender. I tried a different gauge with the same result. Could the wire be bad/ broken?

The speedo cable seems to be seated into the back of the speedo and into the trans. I can turn it by hand...???

I can hot wire power from the battery to the blower and it works, I am getting power at the fuse, I tried a known good fan switch...

Also the brake light stays on after I replaced all of the instrument cluster lamps. THe e brake pedal is way down to the floor. I suppose I need to tighten up the e brake cable (?)