Scrap the wilson idea and start all over.
You need to control the two small wires on the primary glow plug relay.
Take fused power(the same size as the glow plug fuse. And run it to a push button switch. Out the other side of the switch go directly to the relay. Use a new wire. Splice it to one of the small wires.
Then the other small wire goes to ground.
When you press the button(ignition on) the power will go to the relay and make contact. The large wires should not have to be touched.
I would take the wire from the glow plug fuse and splice in a wire of the same gauge to run to the switch and so on.
Forget about your timer.
If you want a light, take a second wire of the back side of the switch and run it to the factory lamp. Like a jumper.