High humidity isn't really a big issue but combined with poor air flow it is a problem. Bacteria and fungus both love poor ventilated hot humid conditions. Your high on the hot and low on the cool try reversing them low oles on the hot end and high on the cool end.
Hot air rises and moves along the lid, the void draws fresh air in the low holes. The hottest air escapes the cool end high holes and the air that has cooled moving across the lid drops to recirculate.
Using the respiration of the snake to increase humidity is crazy. It simply makes no sense. Use you nose if it smells damp and close you likely need lots more air movement if it is fresh and clean smelling like the substrate does it is likely correct. When in doubt, more is better it is safer to error on too many air holes than too few. The two leading herp vets (Rossi and Klingenburg) both point to poor air flow with high humidity as causes of respiratory issues. (bacterial and fungal)