We have similar setups. My payload is 150 pounds higher. I have the EB and 157" weelbase. My dry weight on trailer is 5300 pounds. I've been to a scale, and I am 100 pounds over payload when ready for a trip. Family of 4 and dog.
The truck is stable, and I'm comfortable being within a few hundred pounds of the limits. I'm a cautious driver, my interstate speed is 58mph.
That gives a reference point, but it is all guessing without going to a scale loaded up.
2013 F150, EBoost,4x4,CC, MaxTow
2015 Surveyor 245BHS