Need help figuring out why my rig is overweight

The dry weight likely didn't include propane, generator gas, fresh water in the tank, freshwater in the water heater, fresh water in the pipes, battery or batteries, etc. May not have included awning, AC unit, and other options. I'd guess all of your "stuff" you've loaded in is also heavier than you think. Most people have that same problem, they grossly underestimate the weight of provisioning a camper.