OP wrote:
The Grand Design has a DW of 5785 and a HW of 574
The JayFlight has a DW of 6335 and a HW of 605 (odd)
The Mallard has a DW of 6450 and a HW of 644
Not wanting to get blasted again but my math says after deducting the weight of my family (550) and any camping gear (500-600), I would have enough left to handle the hitch weight of these trailers.
OK - why are you looking at dry weights? Even if you calculated tongue weight for the GD at 5785 * 13% you get 752 lbs.
What it the hitch receiver capacity?
If you want to calculate with dry weight instead of gross weight, at least add 1000 - 1500 lbs for gear to the dry weight and multiply by 13% to estimate tongue weight. If you really want to know what your payload is, load the TV up with family, pets and all the stuff you plan on hauling in the bed, Google Cat Scale Locator" and go get it weighed.
Good luck.