First off 1400lb CCC for that size trailer is a problem. You'll max that out with 6 people worth of food, clothes and gear. That is a very small CCC. Yes that trailers GVWR will be maxed out for a trip! As will the Expedition.
I'm towing a 35ft 9200lb loaded TT wth my V-10 X with 4.30 gears. I'm also using a Reese Dual Cam (StraightLine) system. The X handles the trailer without an issue! He only thing I did to the suspension was add a Hellwig rear sway bar and air bags. I have had 7 (4 adults and 3 kids) people and a 100 ln dog in my X with the trailer and it never complained once! They are an excellent HD SUV (built on the F250/350 chassis). The only difference between the X and the Super Duty is the springs. Put 350 springs under it and you have a SD.
As far as legality goes (I'm sure people will chime in) stay at or under the axle ratings and you'll be fine!