Voltage problems, cutting out when hot

Some of the extra wiring is for the "key in" buzzer and key light. "I don't" need any of that LOL

Best way to check a switch is to look up the terminals on the diagram and check it UNDER LOAD. That is more than a test lamp or multimeter. One good way is to use something like an old headlamp. 'Rig' clip leads on it so you can wire it up. Put the key in "run" and wire the headlamp up to the "run" output wire, and batttery NEG, and wire the battery hot to the switch main wire. Now with it hooked up and lit, wiggle the key to see if it flickers. Take a voltmeter and put one lead on the main wire into the key (power) and the other lead on the "run" wire. This will measure voltage drop across the switch contacts. There should be very little, perhaps .2V (2/10 of one volt) the less the better. Again, wiggle the key to see if it jumps around.