It took me the last 3 weeks of casually looking, but I finally found the output point of these switches at the bottom of the passenger side B pillar a couple of days ago on my '17 3500 HR. I wish I would have found this thread and Dwayneinfo's post about 3 weeks ago... It would have saved some head scratching. Yes, pin 12 is Aux2 and is ignition fed @ 20 amps, pin 15 is Aux 1 is 20 amp and is battery fed. As far as I can tell, they are not "logic level" switches.
I ordered a Tyco connector and pins from Amazon to plug into it. Search part # 1-480710-0 for the plug and 350218-1 for the pins.
Now I have a driver's area switch to shut down the charging to my power inverter via the isolator setup in back, if I want/need to for some reason... But so far, its always left on so the system is charging when the vehicle is on (pin 12, Aux2).
The upfit continues.