Do I have enough margin for safety with towing setup?

This is a case of where you have to use the trailers GVWR. Normally I say to add 12-1500lbs to the dry weight. But here that would be at the GVWR.

But yes the Expedition will handle that trailer just fine provided you set it up properly I.e. 12% tongue weight. That would be a TW of around 780lbs.

IDE be more worried about maxing out the trailer before the Expedition.