I'll look at the wiring diagrams again tonight with this new information. The constant control relay module doesn't come into the picture for the headlights (just fuel pump, A/C clutch, cooling fan, and PCM power). It seems like there might be a highbeam headlight relay somewhere, but I don't remember seeing one in the schematics. It would be possible to disconnect the high beam wires from the headlight sockets, but it would be interesting and recommended to understand where the problem really is in case there is a short somewhere that is a potential fire waiting to happen.
-Rod