The quickest way to test that whole system is to check for voltage at the starter solenoid when trying to crank. If it’s there, then your problem is with the starter and not the ignition switch & neutral safety switch. You can jumper 12v to the solenoid lug and see if the starter cranks. If it does, you have a bad ignition switch or neutral switch. I think at that point you would need a wiring diagram to show pin outs to check the ignition switch and neutral switch to figure out which one.
The quickest way to test that whole system is to check for voltage at the starter solenoid when trying to crank. If it’s there, then your problem is with the starter and not the ignition switch & neutral safety switch. You can jumper 12v to the solenoid lug and see if the starter cranks. If it does, you have a bad ignition switch or neutral switch. I think at that point you would need a wiring diagram to show pin outs to check the ignition switch and neutral switch to figure out which one.