I think you just need to pump up those tires to 44 psi when towing and see how that changes things. If it's still giving you those same feelings, you can try to 'tweak' your WD setup some.. You'll need to know some weights first, so you'll have to run it over a scale and get some actual weights.
Your truck probably weighs more than #5500 when it's hitched up and you 2 in it.. ;)
Probably close to it's GVWR which is probably around #7200.
How was the trailer loaded up? Was this the ride home from the dealer?
If the fresh water tank is above and/or ahead of the trailer axles, try filling it up and giving it a tow. The thought is that should raise your trailers tongue weight and that usually helps with keeping the trailer from 'wandering' around..
I don't think anyone is able to adjust their WD hitch the first time out of the gate... I made my first adjust to my hitch after about 3-4 tows and it made a big difference.. All I did was lower the hitch head one more hole and that was enough to make the nose of the trailer just a tad low in front, but the towing was much better after that.
Good luck!
Mitch