New truck, New trailer, TONS of sway!

I have made tons of adjustments to my WDH. Seems like for the first year I was trying a tweak on every trip. Every adjustment, even the small ones, could be felt in the towing experience. None were as scary as you mention, but I've got less length and weight. Some were "not good" though. I've now settled in on something stable.

All that said, I know your engine is not having any trouble with the load, but the rest of the truck is not up to it.