Adding a new switch and breaker to a portable air compressor

It's amateur hour for this wiring project. I am hardwiring an air compressor to my aux battery. The compressor was taken apart a while ago and I have some incomplete connections. I am replacing both the compressor's breaker and the switch. 1) the old breaker has one wire connected to the relay but the other blade connector is missing a wire. Where should this missing wire be connected to? 2) The relay blade connector (30) in the diagram, is also missing a wire and connection. What should be connected here? 3) the new switch has 3 blade connectors, I think the third prong is for the light. What should this 3rd prong connect to? 4)lastly and the dumbest question of all. The original breaker is a 45 amp 125/250 VAC. I have a new breaker 40AMP 48 Volts DC max. will this work?