Hitch says 3500 lb max and 350 lb max tongue.
IMO you have enough weigh in that van to tow heavier, and I am sure your axles are rated high. But im not sure the weight of the options you have in there..
Your weakest link is that hitch. You need that WD hitch. That will net you up to 500 lb tongue
Tires can be a weak link. post the max tire pressure on side wall and max weight .
But as stated the best option right now before you do anything, and want to know your vans capibilitys... Get to a cat scale.
Get the front and rear axle weights. Do this with full tank of gas and what you may camp with.. kids, clothes...etc..
Post those #,s... Then post the axle weights from the door tag..
Subtract the #'s from the scale from the #'s on the door tag and thats your remaining payload. That will tell you what your truck has remaining..
Let us know..