In the original post I think you said you called and got the payload. I believe I would go to the dealer and look at it myself. It seems awful light. Mine is a 350 diesel crew cab Lariat package but still there isn't that much difference and it has a payload of 3492.
My truck weighs just over 8,000 with just me in it and a full tank. My current setup grosses 19,300 so that put my trailer at 11,300. The is up from a shipping weight of 9300. I am under all ratings but just barely on FA (200 lbs)and GVWR 300 lbs).
Those are real numbers and you can sorta interpolate from there to your plans