There is an NHTSA "safety standard 216" which requires a vehicle's roof to be able to support 1.5 times it's weight but I have no information as to whether it applies to SUVs (or whether the Durango complies, if it does apply to SUVs).
From that picture, expecting that roof to support 7500lbs (curb weight on the Durango is probably 5000lbs) is wishful thinking at best.
