The gross weight of the trailer isn't really meaningful, because you may never load it that full.
You will have, at a minimum, added to the dry weight:
*battery
*propane tanks
*any accessories you add on
*weight distribution hitch
*20 gallons of water = 160 lb (I say this because you want SOME water to travel with, and that's enough to get you through at least one night if you are careful)
*food
*bedding
*kitchen equipment
*clothes
*entertainment such as electronics & toys
Now some people take half the stuff in their house. Some people (like me) travel pretty light. My advice is to start out minimally and add only as NEEDED. Take a notepad to write down small items as they come up.
A good starting point is to assume you will add 1000 lb to the trailer, at the weight it rolls into the dealer.
You may be OK towing for short trips at low speeds on good roads close to your limits. Pushing the limits will not make towing on longer trips a pleasant experience.
The only way to know what you REALLY have is to get some real weights on a loaded trailer.
In your shoes I would shop for a trailer around 5000-5500 dry. Also, don't get a trailer with very little carrying capacity (the difference between the dry and gross weight ratings.)