According to the
2011 DODGE RAM 1500 PICKUP TOWING CHART,
"Maximum Trailer Weight = GCWR - Curb wt. -150 lbs. (allowance for driver) - 20 lbs. (variation allowance)".
The TOWING CHART neglects to add that the GCW also must include the total weight of occupants and cargo added to the TV, in excess of 150# -- including the weight of a WDH, if used.
Per Dodge, the OP's allowable trailer weight,
based on GCWR and OP's cargo assumptions, would be 8900-570-100 = 8230#.
Since this weight probably would cause the TV's GVWR (and, possibly, the receiver TW rating) to be exceeded, the allowable trailer weight should be based on TV's GVWR (or receiver rating) rather than on the published "Maximum Trailer Weight".
Ron