Sticking his had near the screen could be the snake just looking for a way out. If they can find a way to escape they will.
Before adding anything moist or misting the tank I would take the rocks off of the cardboard hide. It looks like a fine hide and I can see you are trying to make it more naturalistic but if the box gets to most it will collapse under the weight of the rocks. Now the rocks may not be heavy enough to hurt your snake but I wouldn't chance it.
Try cutting a tupperware container to make a hide. The hole could even be on top and you could stack the rocks around it for a more natural look. With a container that is wide, short, and flat bottomed you could cut a hole in the bottom. Dig out the substrate to put the container deeper in it and then cover the sides and most of the upward facing bottom to make a hide that seems like a natural cave. If you placed your rocks around it to cover the container it would not be to much to pick it up to check on your snake.