I have a 2011 Ram 1500 2dr 2wd and with the WDH properly setup I don't have any sag issues (my tongue weight is a lot less than the OP)
When I was using the truck itself to haul PA equipment it used to sag and actually rest on the bump stops.
I took the truck while it was loaded to a spring shop and they took some weights and measurements to have a custom set of rear coil springs made up.
It cost about $700 total (installed) and when the truck was loaded with about 2300lbs in the bed it sat perfect as if it was empty.
Since I sold that company and now just use the truck for towing our trailer I had the factory springs put back in.
I noticed no difference in ride with the heavier custom springs installed, might be a option to look into for your issue.