You need tongue weight to increase trailer towing stability. As far as weight on the truck you need to stay under GVWR, RGAWR, and FGAWR. The weight distribution hitch will move some tongue weight to the front axle and some back to the trailer axles. Actual weight is what really matters. Generally if the trailer GVWR is within the tow rating you should be fine. If near max do not expect to carry much in the truck bed. On smaller trucks the frontal area can also sap the towing power to buck a headwind. Yes you are on the right track and forget dry weights unless you plan to transport empty trailers to the dealer.