IMO 4600's are plenty for the F150. I had 4600's on my 08 and Ranch9000 on my 10 F150. It's a PITA to adjust the 9000's. You have to turn the tires each way on the front to adjust them. And you have to lay on your back to get to the rears. I never really noticed all that much difference in adjustments on the 9000's. With the 4600 you just install and you're done.
On the tires just pump up to 44psi, I did all the time before I got some E's. Won't hurt a thing. JMHO but after dealing with my 10 F150 with max tow, I found tires to be the best improvement. Tires will help more with side sway and keep the front planted better than replacing shocks and keeping the marshmallow P tires. Those P tires are IMO good for TT's up to 5000lbs. When you get near the 7000lb range then D or E rated tires make the biggest improvement.