All the info you need is on the labels. On the truck, you have a payload, AKA Cargo Carrying Capacity that shows how much available payload from the factory. That is the empty truck with a full tank of gas. You also have one on the trailer. Take the CCC on the trailer, and subtract it from the GVWR of the trailer then multiply that by .13 to get an idea of what the tongue weight can be at 13%. Subtract that from the trucks CCC and that will tell you what you have available for people and items in the truck. Just remember that everything you add to the trailer can add to that TW and subtract from the trucks payload.
If you are near a CAT scale, you can hook up and take the trailer there and get front, rear and trailer axle weights, which will help set up the WDH.
Goal is to return your empty truck front axle weight with the hitch, so you want weights with and without the trailer attached.
A preliminary WDH setup to get you to the scale is to measure front and rear wheel well height unloaded, then hook up and try to get the front wheel well back to it's original height with the WDH. If you do that, you should have it properly set up, but should be done with the trailer loaded, ready for travel with water in the FWT.
You need the scales to make sure you aren't over the GAWR or tire ratings.
This to me is THE most important thing out of everything you do when towing an RV. A properly set up WDH makes for the safest travels. Everything else is secondary.
