Not knowing what you plan for auxiliary brakes, I can offer only 2 hints:
1. Rather than do exactly as the manual indicates, after you put the Edge in neutral, turn the key back as far as it will go (you can't get the key out unless the Edge is in Park). That way everything is off.
2. Use auxilliary lights rather than tapping into the Edge's lighting system or using a converter.
Regarding how it tows, after 14K miles last year, I have but 1 word.......beautifully (I have to check the rear-vision display to make sure it's still there).
CAUTION: DO NOT disconnect the Edge (or anything else) until you either set the E-brake or put it in "Park". Last year I saw a man disconnect his TOAD when it was still in neutral and the car coasted backwards; only stopping when it hit a "Fiver".
Bob (Squidly Down Under) & Peg - 2013 Ford Focus pushing a 2011 Phoenix Cruiser 2552S
"In God we trust" to preserve our country and bring our Troops safely home.
Carry on, regardless..................