That is a very simple circuit to troubleshoot. if the circuit is grounded, the light will come on.
Start with the parking brake switch. if the switch is pushed all the way in, it should NOT be grounded. Adjust the sleeve in the switch in or out till it does not ground till the pressure is off of it.
For the shorted brake distribution block, your warning circuit is too far to one side, grounding the switch. Start by opening a bleeder screw on one of the front brakes. Press the brake pedal slowly and firmly till the light goes off then stop and hold the pedal. Have someone closed the bleeder, then let off of the pedal.
If it doesn't go off, do the same with a rear bleader. This will push the switch back towards the center-off position, by using the pressure of having one side open.
You have to fix one circuit at a time so leave the pedal wire off when doing the prop valve circuit and vice-versa.