the used 5ver I purchased has a dry weight of 7000, and a fully loaded weight of 8200 (including water) the hitch weight is 1200 and the truck is basically level when hooked up, other than maybe a little slow on uphill grades I would think these numbers look ok??
You have the truck/trailer and have been using it so you know if it suits your expectations. Your call there.
I would say the 7k dry 8k fully loaded trailer with a 1200 dry pin weight that may be 1400-1600 lbs after loading. Now is the time to weigh the trucks front and rear axles weights separately then hook up the trailer and reweigh. That will give you the actual weights and eliminate guessing.
I would guess tho the truck will be very close if not over its 3900 RAWR/P tire and wheel capacity. If so I would purchase a set of higher rated LT C or a D load range tires. Be sure your OEM wheels can handle the increased load and pressures.