Trailer. 1450
Cargo. 200 as stated above
Hitch. 50
TOTAL 1700
Towing capacity 1750
Remaining capacity 50 pounds
I've heard varying info on what is in tow capacity. For instance, is the driver included? is the gas tank full? etc. For the purpose of discussion, let's assume that driver and gas are accounted for in the capacity and that you are not heavier than the assumed driver accounted for in the capacity. That leaves you 50 pounds for a passenger before you hit the max for the vehicle.
I am treating the 3 limits separately, gross weight of the car, gross weight of the trailer and towing capacity, except that I would count the tongue weight on the car; and as long as the trailer has brakes controlled by the driver of the car.
The ratings for gross weights of the two vehicles are set by engineers who understand the strength of the vehicle structures, particularly the axles. Similarly, they have some means by which they calculate the car's ability to pull, but not bear, extra weight. Pulling something on wheels is a lot easier than carrying it, for cars as well as people. I suppose engineers take into account the stresses and strains of bumps, curves, and hills, and build in margins of safety to account for decrepit vehicles, and people who can't resist overloading their wheels (and then publicly boast of) or don't understand towing rules.
I've only found one clear statement online, from Kelley Blue Book which only partly clears up some of the confusion:
“A vehicle’s payload capacity is the maximum amount of weight it can safely carry. In a car or SUV, that includes all of the weight in the cabin and trunk. In a truck, it consists of all of the weight in the cabin and bed. If you’re pulling a trailer, the payload also includes the weight of the trailer pushing down on the trailer hitch — something called tongue weight.”
I've seen nothing from any car manufacturer, and lots of confusion otherwise.
Experience will also be a good teacher for us. Can we go uphill at a reasonable speed, or should we look for a different route? How much more often should we change oil or transmission fluid? Is there more vehicle prep we can do to ease the stress of carrying and pulling our stuff? I expect towing can shorten the life of some part of a car in almost every case, but that's an unavoidable part of the cost, like gas.