900 Watt Solar Panel System - Diagram and Questions

1. 2 Gauge (overkill but you are already using it for step 2)
2. 2 Gauge
3. I am always a fan of soldering.
4. You have no isolation between the chassis and coach batteries. The batteries are of a different type. You will drain the chassis batteries while camping and may not be able to start the coach, let alone damage the batteries due to the constant discharging during dry camping.