Your truck will be fine. I have a 2010 F150 Supercrew w/5.4L. My TT is a 2009 Laredo, 31'. We have been to Yellowstone and Colorado and did great.
I, too, had some issues with sway...I figured out I needed a little more wt on the tongue to help with sway. Much better. My gas mileage while towing ranges from 8-12 mpg.
I also am looking at the 2015 F150. THe 700# increase in payload would be huge. I don't really need the 250 Super Duty, except if I ever upgrade to a fifth wheel in the future....but I have a hard time with the $15,000+ to do it.
