WD hitch and cargo behind rear axle & tongue weight

Me thinks you're a little confused. As Mike said, adding weight behind the rear wheels only subtracts from the payload amount, not add to the tongue weight. Not sure what your truck's payload capacity is, but I would think with a 1090 lb tongue weight, you just might be pushing that limit.

Remember, everything and anything you put in or on the truck itself should be subtracted from the truck's payload capacity....and that includes you.

Ron