Read this caresheet and I would suggest getting the recommended book:
http://www.proexotics.com/care_savannah.html

Humidity is a funny thing with monitors......I don't check it in any of my setups, but range of different humidities are provided via the deep soil substrate.......other things are much more important so get the rest of your husbandry and care squared away first.

...and monitors are not really 'caresheet' animals.....they require much more than a caresheet for success...