Bracket Car Wiring Help

I used the white streaks to erase the wires not needed off of your drawing.
also ... Note the GND (ground) wire off the NSS.

The MSD gets power from the IGN switch and the Solenoid coil gets energized by the push (momentary) start button.
The coil can't get energized unless the car is in neutral (or park) because the Neutral Starter Switch provides the ground patch for the solenoid coil.

One side of the solenoid coil is hot and the other side is ground ... and ... that is in an open state (not grounded) unless the NSS contacts are closed by the shifter lever in the correct position.