^emcvay, your last post sums it up. Everyone's opinions of what they're comfortable with vary widely and I'd hazard that those that know their way around things mechanical and those that "drive stuff" for a living or for recreation are/may be comfortable pushing the limits of a vehicle further.
Since your a gear head, you obviously should understand what goes into the gvw rating of light trucks and also how those trucks are constructed.
Stability of a dually can't be denied, but for you it may not be "necessary" for someone else it may be.
I'm running what I would expect would handle about the same as a 990 on your long bed F350. Never had issue with it. Maiden voyage with a 4000lb camper included towing a 6klb trailer 2400 miles to Alaska. Slapped some airbags on the back and pumped up the 3950lb rated Toyos to 80psi and hit the road.
Was it like driving a fun house at times? Yes. Did it bother me? No. Even my wife drove it, so it could t be THAT bad.
Since then, I made some lower "stable load" wedges and added a sway bar. I think it handles pretty decent now for what it is. Haven't found a road that I couldn't keep the same speed as the speed warnings going into a curve. Can I rip through a "45mph curve" at 55 or 60 like if the truck was empty? No, I don't think so, but that's what the warnings are there for IMO.
OE tire and wheel loading WILL be exceeded a bit as you know. Figure 4500lbs centered over the axle as a good round number for the load. I believe right or wrong that the OEs put a huge factor of safety in wheel and tire ratings. Why? Because the liability outweighs the reward of saving a couple bucks on wheels.
If your comfortable wringing out a race car on a roundy round track, hauling a camper probably won't scare you...lol.