Welcome to iRV2. You will find loads of good information here.
On your towing question, the 9200# rating is a maximum for the truck based on a base model, no cargo, only a 150# driver and no trailer hitch. You add accessories, cargo, passengers, etc, you need to drop the tow rating pound for pound.
is a good site to explain all you need to know about towing.
First you need to determine if the 9200# applies to your specific truck, engine and axle ratio. As a starting point use 80% of the tow rating as an estimate fro a loaded trailer you can tow. So we start at 7360# for a LOADED trailer...forget dry or unloaded weight as published in the literature. You can easily have 1000# over the unloaded weight.
Your tongue weight can be 10 to 15% of the trailer GVWR or in your case the dry hitch weight is already over the estimate, so figure 864/6107 x 100% or 14%. 14% of 8058 = 1128#.
You need to weigh the truck with all normal cargo and passengers, full fuel.
GCWR - loaded truck = max loaded trailer weight.
GVWR - loaded truck = max trailer hitch weight.
I doubt if your Expy has the capacity to haul an 1128# hitch weight and be with in ratings.
Next issue is the length of the trailer and you will get lots of opinions here. People pulling like trailers say no problem, but they will not offer to supply any weight numbers for their rig....they don't have them. Personally I feel that that is too long of a trailer for an EXPY.
Now that I have rained on your parade, the best advice is to weigh the truck and see how much trailer you can pull within rating.
The Hensley is a great and expensive hitch...but it does not cure an over weight or a poorly matched rig. For a lot less $$$ the Reese Dual Cam HP will work as well.
Educate yourself and believe nothing the RV or truck sales people tell you.