We towed our X23B with the '03 Expe 5.4 and it was adequate, but just. The max tow was around 9500# and the HTT scaled in around 4400# with 600# on the hitch IIRC. My surprise was with the Bride and me aboard we were abt 300# shy of the Rear GAWR. With another couple and their "stuff" we would be over on the rear axle but still well under the max tow #.
My point is, don't go by the max tow wt.
From your posted TT weights you could estimate the TT GVW and tongue wts which will give you a starting point. After you get the new TT a visit to the scales will help you understand how you are loaded and if any tweaks to the WDH are needed. There are a couple of "stickies" that discuss how to weigh and how to interpret the results.
The CAT Scale is your friend.
2013 F-350 CC SB 2WD 6.7PS
2013 Eagle Premier 351 RLTS
-SOLD- 2012 X23B
-SOLD- 2003 Ford Expedition 5.4, Bilstein shocks