If your manual says you can't use a WDH then don't. Correcting rear squat is not why you use/need it. Putting weight back on the front wheels to restore steering control is why you do need it. So the question is, do you have the same control over your steering when the trailer is connect as when there is no trailer? If not, then you need a WDH.
This might be the hitch you need. If nothing else, call them (Etrailer.com). They will know if the correct hitch is available for your truck.
The effect you feel when trucks pass is normal no matter what you tow, and in fact increases with larger trailers and tow vehicles. Watch the side view mirror for passing trucks and learn how to prepare for it. You really do get used to it.
You're running 70? The ST tires on your trailer are rated for 65. Faster speeds increase the heat on the tires, which increase your chance of tire failure. Most of us run at 62/63. Tires run cooler, the entire rig is easier to control, you give yourself more time in the event that there is something going on in front of you, and you increase your gas mileage.
A small trailer needs sway control as any other trailer does. Sway control is like your car insurance. You may go 20 years and never need it. Then one day something out of your control happens and it's all over. Sway control is cheap compared to dumping your trailer.
Chuck D.
“Adventure is just bad planning.” - Roald Amundsen
2013 Jayco X20E Hybrid
2016 Chevy Silverado Crew Cab Z71 LTZ2
2008 GMC Sierra SLE1 Crew Cab Z71 (traded)