Remember that you are dealing with Relative humidity, that means that the same amount of moisture in the air will read different numbers at different temperatures. First stablalize your temperature, use the setup just mentioned if you need to.
Then test your hygromater at the temp you will be using it at with a salt test or kit. Once you know it's accurate at that range then adjust the humidity.
Understand that if you open the door on a humidor that big and empty it will take a very long time for beads to stabalize all that air. Empty cigar boxes will help, but filling it with lots of cigars will help the most. Start with one's you will not cry over if they split a foot or dry out and see how they feel after a week inside. It sucks and I know you want your new toy all done and happy, but these things take time.