You need to do the headlight harness, if you have not already.
The wire from the headlight switch THEN becomes a trigger wire to the aux light relay.
You will THEN have two completely different light circuits operated by the brights switch on the steering column that are independent of each other but operated by one switch. One to the headlights and one circuit to the aux lights, neither are receiving power from the headlight circuit itself.
Tap into the brights wire at the headlight and run that to the trigger of the relay.