emcvay,
The exhaust brake on my 2006 F350 6.0 SRW works in tow/haul. It changes the way the motor sounds enough to know that it's more than just a downshift, probably turbo involved as described. Very handy for easing down into King's Canyon with my Wolf Creek : )
My rig is weighted perfectly for my truck in my opinion, and that's the only opinion that has real validity for me. It is the "seat of the pants" meter that makes that determination and I trust it. Panic stops are controlled enough that I am comfortable, though my driving habits are much more conservative when it is loaded. The difference between loaded with empty tanks and full tanks is noticeable, so I usually keep it empty for as much as possible when traveling, but heading out with max fresh water is sometimes unavoidable. Trips home on empty tanks are stress free. I have both types of StableLoads installed and they work very well. My rig actually handles better with my little 8X5 enclosed utility trailer, and full tanks help when high winds are blowing.
My wife and I spent a lot of effort outfitting the camper with lightweight gear. Down sleeping bags, Lexan cutlery, plastic plates and cups, aluminum cookware, almost no books or heavy things like shoes, boots, etc. We managed to keep our extra stuff down to a minimum and try to load any extra items into our trailer when possible (dutch oven, hibachi, canopy, telescopes, ATV, prospecting gear, or whatever else we intend to do). Most of our trips are themed so we don't carry anything unrelated.
Performing due diligence when researching a new camper purchase and matching to an existing truck goes with being responsible, taking what dealers and friends say with a grain of salt is usually smart too. Only you will be saddled with the fallout from an overloaded set up that you may not be happy with, and only you can take steps to fix it. You won't know unless you drive an identical rig beforehand, so lacking that, you are still willing to take the risk - so be it!
As stated before, coming to this forum and asking questions will yield a forest of opinions, and somewhere in those responses might be your answer. It sounds like your head is squarely on your shoulders but it also sounds like you are trying to convince yourself that your numbers will work out okay -- they are what they are. Your experience as a tenured TC owner should count for whether things will work out as you plan, unless "buying fever" has made you blind.
My opinion is worth exactly what you paid for it. I wish you all the best in your experience and will be interested in how it all turns out!