qarma

Another problem is the siege army -- medieval armies were not supplied well and it's reasonable to assume soldiers will pillage nearby villages, then hunt in the forest; thus the tunnel outlet is likely to be discovered. In addition, siege force will have scouts and lookouts spread over wide area to warn of potential relief force arrival. That all being said, it makes sense to try and build a tunnel. Usually, in the medieval times, smugglers would bribe the opposing army to let the trade continue.

If a moat surrounds the castle, water will be a problem.

No brainer: go and get your Master's degree. It is in the interest of your employer to part amicably because then you may consider working for them again when you graduate, when you are "smarter" after you'll have invested time and money in your own education.

Please cite better sources. naturalnews.com might sound legit, but their content is total FUD at first glance. Which meant I never took the second glance.