If your water bowl is directly under the CHE then the CHE will be sucking the moisture out. If possible it would be best to have the water bowl away from the CHE. More substrate can deffo help to hold more moisture but only if you use the right substrate. I would recommend coco husk mixed with eco earth. Something like Aspen does not hold humidity well.
I think if the humidifier is the only way you're able to get the range you need then you might need a higher wattage CHE on your hot side. Changing the bulb out shouldn't be too much trouble.
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