The long ton is used for petroleum products such as aviation fuel. Deadweight ton (abbreviation 'DWT' or 'dwt') is a measure of a ship's carrying capacity, including bunker oil, fresh water, ballast water, crew and provisions. It is expressed in tonnes (1000 kg) or long tons (2240 pounds, about 1016 kg).
Trains between Naples and Sorrento depart once every half hour and take about 55 to 68 minutes in duration. Thus, to get from Rome to Sorrento, you would first take a train to Naples, where you would switch to a Circumvesuviana train down to Sorrento.
Sorrento to Salerno is actually pretty far maybe 30 miles or so and what slows down a car/bus trip along the ocean SS163 road are the curves which from Positano are practically non-stop. If you get car sick easily, you can consider taking the Circumvesuviana Train from Sorrento to Pompei Scavi/Villa dei Misteri.