First thing I would do is slow down to 60 mph. I would not want to tow at 65 with your TV and that TT.
You should not need a fancy WDH to fix your problem. It sounds like something is not set up right. Which Reese WDH is it? Lot's of people tow a TT that length and weight with an F150 without issues without resorting to an expensive hitch. Depends on how your F150 is optioned for towing too.
It would help if you posted the weights you got from the scale. Photos would also help. Without seeing the numbers, I'd guess that your spring bars need to go up one size. If undersized, you can't transfer enough wt. back onto the steer axle.
Don't rely on the dealer to set the WDH correctly. If it's a dual cam, chances are high that the dealer has it wrong and maybe really wrong. Have you measured the before and after front fender heights? You need to look at the hitch manual to see what it says for what the restored front fender height should be and also what Ford says for your F150.
Is the trailer level when hooked up? It should be level or slightly nose down. Have you got the tires in the TT and truck inflated to the correct pressures?