I too think you've got more trailer than you'll be happy with. If you can still back out of the deal and go to a smaller trailer, do it! A trailer that is too big to enjoy towing and rarely gets uses is worthless, compared to a trailer that may not have as much comfort but gets used more often. My prior trailer was at the limits of my prior tow vehicle and it was no fun and almost caused an accident, which is why I purchased the TrailCruier 30qbss, which is a 30' ultra light, lower profile trailer for the Expedition.

I'm very happy with this combo, and would not want anything longer, heavier, or taller when towing. Length is PITA to park, fuel, and get into campgrounds. Height or frontal area is underestimated for the wind drag it will cause at highway speeds. This will slow you down, kill you fuel economy, and make you more susceptible to wind sway.

I weighed my trailer at a truck scale and this is what I found (with only a driver).

Steering Axle #3500
Drive Axle #3900
Trailer #5220
GCVW #12620

I’m only about at 86% GCVW capacity, compared to your >96%. You will be overloading your axles too. Not sure where I found it, but I found the ratings to be #3700 front & #4250 rear. My goal for the trailer/truck combo was to be #2000 less than GCVW so I had enough power for the mountains, not to cause extra wear on the TV, less stressful towing experience, and most importantly safety for my family. I have a documented 9,800 tow miles with this expy & trailer so I'm speaking from a bit of experience.

I think the 2011’s have a heavier duty transmission than my 2007 but I do have the 3:73 gears which help with the towing power. I have added a transmission temperature monitor and have the Tekonsha Prodigy brake controller which I highly recommend.