Not planning on losing my down payment. I don't know about the rear axle limit, but here's one thing I think everyone's forgetting about the 5th gen rear axle and that's how beefy these are for a 1500 truck. I do know for absolutely sure the tow rating on my truck is damn near 12,000 lb. Would I tow that amount? Hell no, & I don't want to tow anymore, been there done that. No more trailers. But, I think with the tow rating like that it's beefy enough to push it over a thousand pounds with all the suspension mods I'm planning. Doing all the suspension mods in stages to get it where I deem it functional.
I'm not giving you a hard time, just describing how it works.
Your tow rating is a myth. There are 4 important limits on your truck:
GCWR (what you can pull, and thats the 11k to 12k limit you noted)
GVWR (what your vehicle can weigh, most people use payload instead as its easier to do the math)
RAWR (rear axle)
hitch
The first limit you exceed, that's the limit on your truck. If you're pulling a boat, it puts 5 to 10 percent tongue weight on your truck, you can probably pull 10000 pounds which puts 500 to 1000 pounds on your truck leaving 200 pounds for driver and a bit extra for passengers + cargo.
If you're pulling a 5w, they typically put 15 to 20 percent or more on your bed, you can no longer pull a 10,000 pound 5w. That would put almost 2000 pounds on your truck + another 100 pounds for the 5w hitch itself.
So Ram doesn't know what you're pulling, thats why they give you multiple limits, and the first limit that you hit while pulling/carrying whatever it is you're doing, that's the limit.
Most people are limited to about 8000 lbs or less when it comes to common trailers. 5w's are pretty much not towable, and neither are slide in campers. You found one of the very lightest out there, but the important spec not to go past is the rear axle. It's rated at 4100 lbs, but you may want to run over a cat scale. There are a number of stories of guys bending their frames carrying/towing too much weight, especially offroad which really leans the truck and forces the weight temporarily over one spot.
Suspension mods don't help you carry additional weight beyond your original GVWR, they just control the weight you do add, better. Your payload is your payload, and no suspension mods you can do will fix that unless you start modifying the frame and rear axle as well.
But I'm not going to argue this to death, just letting you know a number of guys have wrecked their Rams/frames doing more then they thought it could do. If you bend your frame or damage it with that camper, Ram will deny you warranty as there is no way you can carry it with a driver and still be under payload.
(don't shoot me, I'm just the messenger 🤷♂️ )