ok the wate bowl sounds fine depending in the size of him but from you description it seems fine and for the humidity i have a 60 gallon glass tank and glass is verry dificulto to keep proper humidity and temp so what i do is cover the hot side of the screen top with foil and cut a hole in it for the light and just cover the cool side with a dry t shirt or thin sheet for ventilation and mist the all the plants and substrait in the mornig so the foil keeps the heat in and the shirt traps the hmidity.
also i would not recomend using a wet towel cuz it can transfer bacteria into the air of you snakes enclosure.