Is there a schematic available for the headlight circuitry?

There should be continuity from fuse to light if the circuit is connect properly. Are you getting proper voltage to fuse?

How many fuses have you tested? Do the high beams work in both the normal switch position and 'flash-to-pass' position? EVER any front end body work? Check/test for proper GROUND on BOTH sides-with voltmeter. AT THE FUSE LOCATION in the under-hood fuse box , test both left and right low beam fuses for the correct 'switched voltage' (have a helper turn the switch on and off).Repl with results for more.