General comments:
Make sure your hygrometer is calibrated:
http://www.cigarsinternational.com/html/cig101_12st.asp And digital is good, analog flakey. Even after I calibrated my analog, it keeps changing whenever bumped or something. Some day I'm going to take it out to a lake and see how many skips I can get with it.
I've had some issues with 50/50 myself. Cigars inside the 'dor, and cedar, do seem to help stabilize the humidity. I don't understand why that matters, but it does.
Airtight is better. For example, you wouldn't want you winter-heated 30% humidity house air sucking all the moisture out of the 'dor. I'm sure you'll open it once in a while to freshen the air.