I still use two glass tanks. One is my Hoggy and the other my Ball.

Both have most of the top screen covered. The Hoggy has a heat lamp so the spot right under he light is not covered and allows for air transfer. The Ball used to have lamp overhead as well but now that they are all in one heated room I took them down. I left the holes that the lights were over which again allows for the air transfer.

It sounds like whatever you are doing at night works fine so try leaving it open and see what happens. If it drops low try the moist moss in the hides. I don't even pay attention to my tank humidity in my Balls setup anymore. I know the hides are giving her what she needs and I leave it be.