Didn't read the whole thread but I have a 2012 2500hd long bed ext cab chevy 4x4 and tow a living quarters cargo trailer very similar to the OP.
I have towed it with and without a WD hitch. It tows a fair amount nicer with the WD hitch. I have had it on a scale once with the WD hitch and with the hitch with 1400 lb bars snapped up pretty tight the truck had within 40 lbs difference betweent the front and rear axle.
With the WD hitch and friction sway control it tows like a dream. Just got back from a 620 mile round trip weekend to Fishers ATV reunion and most of the time was driving with one hand on the wheel just as stable as can be.