[scarceller]

Unplug the harness from the back of the ignition switch.
Jumper Pin 30 (RED - Main Power) to Pin 50 (Yellow - to starter solenoid)

This should engage the starter, does it? and does it disengage when jumper is removed?
If the above test works you most likely have a bad switch.

And as already mentioned remove the AC relay as well and retest, since the AC relay gets it ground from (via) the starter solenoid. The reason it's wired this way is so that the entire AC system deactivates during cranking to help give max amps to the starter.

Also you don't need to remove the entire mechanical ignition switch. You can remove 2 screws from the back of the dash that hold the electrical portion of the switch to the mechanical portion. You need a 'L' shaped Philips screwdriver for this task. It's tight but can be done.