This page has some of the best info on what's okay for beardies. Almost to the bottom of the page is a list of known safe plants. Just remember that whatever you put in there will most likely will be munched on at some point and it's really important to either buy organic or allow 6-12 weeks before placing in your Viv.
That humidity would be correct if they are ina desert area, like I am. My accurite thermometer's humidity reads "lo" most of the time, which is under 20%. It only gets higher in the monsoon season which we are entering now. Then we get anywhere from 35% to 51%. The 51% is very rare and was seen (as I remember) only the year before last.