I recommend these hide boxes: https://www.reptilebasics.com/hide-boxes
For the humidity I would cover the screen on top of the cage about 3/4 u can use just about anything to do this. When I use cypress mulch in my 2'x2'x2' enclosure I wet down the substrate. To do this I do one of 2 things. I either spray down the cypress until its soaked on the top layer, and then move it all around, and spray again lightly, or I grab a cup and slowly drizzle the water on to the cypress agitating it as I go to try to wet everything evenly. I was able to get the humidity to about 80% when needed using this method. You can play with it to figure out what will work best for you though.
The one good thing about humidity is that if you make too much all you have to do is remove whats blocking the screen, and it will drop like a rock.