I towed about a 7000 pound package with a late model Tahoe. Granted mine was 2 door, so the wheelbase was shorter, but it still was not safely enough truck. First off, you are way over your tow rating anyhow, which is going to get you pretty much canned in an insurance claim should you have a wreck. I first recommend a couple million dollar umbrella liability policy over anything you have/do.
Second, if you must tow with this vehicle for a while. Upgraded brakes, cryogenically frozen rotors, with ceramic pads will help you with stopping. What's the braking system on the trailer? Adding disc brakes to all three axles on the trailer with an electric controller would be the cats-ass for ANY towing situation, but you will need to price that out. As for suspension, and truck sway, I believe your Escalade has a load-leveling system to adjust rear end height and all that jazz. I doubt it is beefy enough to handle what you are about to throw at it. I would look into a set of Air Lift air springs for the rear end. You can invest in a full on board compressor for on the fly adjustments, or just run little air fittings out the back of the truck as I had done, and run a flat pressure of 45 pounds in them. ( I now have a 2500 Avalanche, and put the 1000lb. capacity Air Lift bags on this truck too, and they are byfar, a GREAT investment for ANY towing job).
My 8.1L only has 340HP from the factory, but what you need in towning is Torque. The 8.1 has 455lb/ft. Since then I have bumped my numbers up a bit with bolt ons. I drove two very similar packages to your truck before purchasing mine, the Sierra Denali and the Escalade EXT, with the HO 6.0L. The biggest problem with that motor is the powerband and torque curves are VERY high, so it makes all its power, especially the torque at high RPMs. Its like towing with a 2 stoke dirt-bike. Not good.
You have a really great truck, however, I think you might be a bit better off with a 2500HD or 2500 Suburban. There is no subsitiute for cubic inches of big block, and diesel... ha ha, nothing better.
If you want, send a PM to "OutlawMark" or "skater" here on OSO, and they can help you with air bags or other helping items at Outlaw Motorsports up in Culpeper. I HIGHLY recommend them. They did ALL of my work.