Never said he needs a 1-ton dually only indicated that the combination they have is something that cannot be towed safely...
True, but you also didn't provide anything to back up your statement, probably because there is no valid reason why it can't be safe.
If the 3500lbs came off the sticker in the TT then it is the shipped weight as delivered, including options. Loading it conservatively with 500lbs of stuff would put it in the neighborhood of 4000lbs which is well under the 5200lbs tow rating. It's even less than the 80% that many of you preach. A tongue weight of 13% would be under 600lbs so even after adding in the weight of the WD hitch there would be plenty of payload left in the TV for a small family. A 20' TT is also not an excessive length even for the short wheel base Explorer.
So tell me again what's not safe??