1. The WDH does in fact transfer a good % of the tongue weight, split to the front of the TV and the trailer axles. There is no magic number however, because the % transferred either direction differs among every set up WDH set up. More so, the length of trailer and TV wheelbase (different axle distances from the hitch) changes how much goes where. ONLY a scale will tell you exactly how much is transferred, and where it went.
2. While its good practice not to cheat the payload rating with the WDH, because actual weight is in fact transferred, you absolutely can use the WDH to work the payload rating in your favor. But again, there's no accurate math to work this out, you must used a scale to check Gross Weight, Gross Combined Weight and Axle ratings. Only the person towing can say if they feel ok doing this, as it is fact and legit, but it is not a recommended practice.
