1300 lbs is not uncommon for the pre-2015 trucks that did not have max-tow. Even XLT's were in the 1300-1400 lb range.

Nowadays, I am not sure you could even get an F150 that low except for maybe a Limiter or Raptor.

 

10% with an RV is asking for trouble. The most common trailer that easily tows at 10% TW are those with axles past trailer center like flatbeds, horse trailers, car trailers, boat trailers, etc. RV's have mid center axles, which moves their pivot point further forward towards the truck making them more sensitive to sway, so you want as much weight in front of the axles as possible for a stable tow. Toy Haulers especially need to be properly balanced. They may tow extremely well when nothing is in the rear and light on the ball, but will become a sway nightmare with something in the back.

When I got my first RV, I towed it home with a 2014 F150 and it was very light on the nose since it was a bunkhouse. That trip home with it empty was a handful and left me sweating it thinking I miscalculated something. I spent several days readjusting the WDH, and adding a sway brake to it, then got it loaded for the road. Once I got the trailer to 13.6% TW, it towed very well, though the truck was several hundred over gross, requiring us to take a second vehicle for passengers. It had 1450 pounds of payload and the trailer weighed 6400 pounds loaded.