According to the RAM, the weight of the van and maximum payload capacity in pounds is:
Weight of Van - 4895
Payload Capacity - 3940
Total Weight 8835
The current weight of my van with a full tank of water and gas from the scale at the county dump is 7380
This means the current payload is 2485 leaving 1455 available.
If you subtract maybe another 445 pounds for 2 bodies and bags, the estimated available weight would be 1000 pounds.
Each gallon of water is about 8.3 pounds.
Can a Dodge ProMaster Tow a Travel Trailer or Popup Camper?
The Ram ProMaster can tow up to 6910 lbs. The 2021 2500 can pull 6800 lbs. It can carry 4680 lbs of cargo.
It has the towing capacity for campers weight by type: travel trailers 7300 lbs, popups 2500 lbs, teardrops 1200 lbs.