I will get flamed for this, but turn off the electronic sway control on the truck. It is not designed for those big trailers and over corrects and gives you the wiggles. That, fully aired up tires and correctly adjusted WDH (per the manufacturer instructions) will all make it better. Know it will never likely be perfect. Towing a tongue pull trailer is always going to mean a little movement. The only real way to solve that is to go to the ProPride P3 or Hensley Arrow; they work by correcting the physics.
Current TV:'14 F350 Lariat CrewCab, 4x4 Short Bed SRW Diesel w/ Pullrite 2700 (16K)
Current Fiver: '15 Puma 295BHSS Anniversary Edition
Past TV: '13 F150 HD Payload SCrew EB, '08 Tundra CrewMax 5.7L, '02 'Burb 5.3L, '97 Dakota 3.9L
Past Trailers: '09 Wildwood LE 27RB, '02 Palomino Yearling RL, '87 Jayco 1006dlx