Your math a little off
Math would be
gross weight of vehicle loaded for your trip, (full tank of gas , all passengers onboard) plus hitch weight of trailer (if unknown estimate at 15% of gross laden weight of trailer) must be less than the GVWR of your truck
IN ADDITION.
The gross weight of your vehicle PLUS the gross weight of the trailer should not exceed the gross combined weight rating.
All should be weighed/estimated with a full load of camping gear/ clothing and water in the tank.
You need to get most of the numbers off your tow vehicle
