There are a few different weights that must be met for safe towing.
GCWR is the combined weight of the 'Burb, TT, and everything in them. If you cross a scale with all passengers and cargo, the total must not exceed GCWR.
GVWR for the TT and TT, separately. The fully loaded 'Burb including all passengers, cargo, WD hitch and TT tongue wt must not exceed the Payload per the Yellow Placard. The weight of the empty truck plus the Yellow placard payload should equal the truck GVWR. The weight of the TT, not hitched to the truck must not exceed the TT GVWR. NOTE: These two weights may exceed the truck GCWR because the TT hitch weight is included in both weights, thus included twice.
One other way to do the calculation is to start with the Max Tow rating, which is for a base model truck with few options, two 150# passengers and a full fuel tank. From the Max Tow, subtract the weight of all passengers in excess of 300#, the weight of all cargo and anything else in the truck, and the weight of the WD hitch. That is the REAL Max Tow for your truck.
That TT will likely exceed every one of these numbers once you are packed, ready to travel. And this leaves no safety factor, either. CAN it be done? Yes. People do it every weekend. SHOULD you do it? I certainly would not put MY family at risk in that type of situation!