I'm sorry to hear about your ball. I can't help with the mouth rot as I don't have any experience in that area. Below is the humidity gauge I use and also a test kit I use to calibrate it. If you use this particular one, don't use the adhesive attachment that comes with it to mount the gauge. Use either small magnets or a hot glue gun.

http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1
http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1