Dirt will increase humidity, they can grow to 6 feet and are very aggressive. They are escape artists as well and very smart. That won't last very long I say maybe a month if temp and feeding is right, don't really worry about humidity keep a water bowl large enough for it to submerge it's whole body, (you need a basking area temp 80+and a cool down area temp >75)What are you feeding it? If crickets use a calcium supplement to dust on them.