Start Towing with 114K miles on my Yukon?

[swathdiver]

I do have the integrated controller and tow package, so he was hooking up the power to it, which was bundled under the hood.

I may be wrong about this, but I don't think you need to hook that Red/Blk wire to the fuse box post to energize the Intergrated Brake Controller. I think the +12V that is supplied to the +12V on then receiver hitch plug is already there when you have JL1. That line is to power an on board battery in the trailer (usually used for emergency brake application is the trailer brakes away and also dome lights in the trailer, etc.).

As mentioned earlier, the ITBC is already hooked up and fully functional. The wire that was bundled under the booster was to provide "hotel" power to the trailer to charge the battery, run the interior lights, fridge, etc. As long as the 7-pin is connected, engine running or not, it supplies power to the trailer. On the 7-pin connector, this is the black wire at the 11 o'clock position.

I suspect your stabilitrak issues are something else.