Just a heads up -probes do not measure humidity. Probes only measure temperature. The device itself measures humidity. As for the use of a damp towel, remember that it will need to be replaced or cleaned daily. This is because the warmth and dampness in the towel create bacteria very quickly. So Simply change the towel all together or wash the towel in hot water with soap and rinse.
I am glad you are enjoying your snake but before you get another snake you should be 100% sure that you have the funds available for vet visits and proper housing of the new snake and your current one. You should always have your enclosure set-up and tested prior to bringing home your snake so that it does not have to endure husbandry issues (i.e humidity problems).
Now that you are aware of the care required by a ball python, get your current set-up running smoothly - then consider another addition. Do not be afraid to ask questions, no matter how silly they seem as we are all here to help. Welcome to the site!