My problem with your current set up is that the mold spores are in the soil. You really need to dump it all out and start again. Once your jar is cleaned out (washed and sterilized), you can make new layers with new medium. Once planted, I doubt you will need to water it for years. Make the bottom layer charcoal and gravel.
We used to grow terrariums in 5 gallon water jugs (before they went to plastic). After planting, they didn't need any water. Ever.
