Newbie: 1/2 Towable Cross Country Trip Suggestions

This will give you good, unbiased information about towing. Clicky
Basically, what you are missing is the tongue weight when the trailer is fully loaded. For a ball park number use 12% of the Gross Vehicle Weight of the trailer. That will get you approximately the "real" tongue weight of the trailer as it is going down the road.
Doing the math backwards, you should be looking for approximately 6200 lbs trailer (empty weight), which will end up being about 7300 lbs loaded weight, and 875 lbs tongue weight.