I agree with M²Mods, better to use headlight switch. Using the dedicated headlight switch runs it through the fuse box, wiring from the switch to box is factory designed for that purpose, and eliminates any problems that could come from a general use set up and makes it easier to troubleshoot if a problem arises.
You can get the switch from Benny at allmoparparts, the wiring harness from M²Mods and also get the factory wiring connectors that connect from the end of Mike's harness to the fog lights.
I did, he only does harness connected to headlight switch. Actually he was against hooking to the auxiliary switch but didn't elaborate why.
Long story short, I've got all the details worked out to fully support folks with the factory Foglight switch and wiring setup which I have actuallly put my own hands on with someone's truck before.
Unfortunately I just don't have the free time with existing orders and support, to look into tweaking it for a more custom setup I'm not totally familiar with. ...
As discussed, you could get the bumper harness and BCM extension harness I offer and modify it to go to your aux system... But you'd have to determine what's needed for that.
Edit: fyi...
factory setup has 2 separate outputs for each light (monitoring if they go out), will come on automatically at night, can drop out with high beams (or not with AlfaOBD setting) and the output can be enabled for LED (12v constant) vs Halogen (12v pulsed/pwm).
The Aux switch I believe is a single 12v output with no monitoring and the 2 separate fog leads would likely need tied together/to it. Not sure if it's a constant 12v or pwm output.