I'm not seeing where you're calculating the total weight on the TV axles. You have totals for the WD hitch, but no recalc for the passengers and gasoline.
Frankly, this is total overkill, and well into OCD territory. Gas up the truck, load up the trailer, and drive to your nearest CAT scales and get a weigh. Odds are you're fine.
On a half-ton Burb, the weak link is the rear axle. Keep the weight below 4000 lbs, and if you're driving long distances, check the temperature of the axle when you make stops. Yes, I would crawl underneath the truck and feel the rear axle - a digital/laser thermometer works wonders.
Ask me how I became so paranoid about the rear axle of a Suburban. Take a guess. It's also why my current Burb is a 3/4 ton.
