Need some help on how to pin my dizzy

I have a junkyard dizzy in my 78 280.....

My advance is not working so I thought it would be a good time to pin the dizzy at full advance.....I plan on using a machine screw to lock it at full advance......My question is this.

I have a timing light with the dial on the back.

At what RPM do I need to set the timing?

What setting do I need to set the dial at on the back of the timing light?

How much before top dead center should I set the timing to?

And last but not least......

Will doing this improve the performance of my car?