I'd start with the wiring diagram. Make a paper or scanned copy and trace in the wire colors for everything that's effected/not working right. Then make a simplified version (or digitally erase the rest). Take each item back to its power source. It will either be fused or through the headlight circuit breaker.

Then you can figure out what should be hot (on). Since some things are hot when they shouldn't be, you can then figure out where (which wires/switches) they may be getting power from. Then you'll know where to look.