[TJ]

Among the good advice you are getting, have you checked all the connections to make sure they are clean and tight? Make sure all connections are clean and tight at the circuit breaker. Then check all of the bullet connectors at the headlights and tail lights. You are getting as lot of resistance(heat) which usually means loose and dirty connections. I suspect the dimmer switch as it's mounted on the floor where dirt and moisture can enter the contacts on the switch and cause corrosion. Also how old is you're wiring?