I don't think this is going to be an easy fix or even trouble shoot but here is what I'd do, disconnect the batteries, remove the fuses and using your multimeter, check for continuity between the load sides, it would seem that would be the case, now disconnect the wires and check the load side of the fuse, probably no continuity, that rules out a short between the two circuits on the board. Now comes the really fun part, check the two load side wires, should be '0' ohms or shorted. My first question would be are the wires identical? It's hard to tell in the photo, are both white or are they different colors?
If ten is the awning and a different color from one it is after build most likely, beg, borrow, steal or buy a fair to middling signal tracing devise and hook it up and start following the wire for the awning. To make sure you're following the correct wire start at the load and work back to the fuse. If the awning wire is a different color than the lights, it probably is an after market item and the wire may not be in the factory loom.
One step I forgot is to disconnect the wires at the load, the lights and the awning and check for continuity between the wires.
