That 3785lb is the published dry weight, but your actual trailer will weigh considerably more than that (depending on packages/options). Usually in the ballpark of 400lbs more, not including the battery weight. Either way, there is still plenty of cargo capacity. To give you an idea, mine is 4200lbs.
Is your truck the 4.6L or 5.4L? 2WD or 4WD? Gear ratio? The reason I ask is because I pulled mine with a 4.6L 4X4 with 3.55 gears and the 4-speed tranny and I have already bought a new truck after 1 season of that. Even though it is a relatively small and light trailer, it's still full profile and aerodynamic drag is considerable at speed.
The fresh water tank is right above the rear axle, and black above the front, so if you have to haul with water it doesn't affect loading all that much. The furnace and AC are plenty powerful for a unit this size. All in all a really nicely designed trailer and efficient use of space!
I have a good list of mods on my trailer already, but ones I will recommend right off the bat are a MaxxAir vent cover, X-chocks, fridge fans, and a Rhino sewer hose.