Nether Castle

Originally made in my Single Player, peaceful world without inv-edit, I made my world a private, Multi-Player world, and continued making it with the help of my dads leftover cobblestone (everything is obtained without commands).
The castles purpose is to be a safe entrance from the nether, and to insure that there is a safe place for one to stay in the the nether.
The landform this is built on is called the mushroom, and pretty much looks like a upside down mushroom, hanging from the top of the nether(that is only supposed-it could also be a huge landform, maybe even a floating island! The castle goes around the edge of the mushroom. It also attached directly to the stem(I think it might also called the stalk. I dunno? Or is the stalk the circular part of the mushroom? Or is that the cap....if you know the answer...feel free to comment and help me)
At the thickest, the Mushroom is about 8-9 blocks thick, usually about 4 blocks thick, and at the thinnest, 1 block thick. The area near the portal is about 1 block thick, and other parts of the castle are about 2-3 blocks thick. If my brother doesn't stop attacking the ghasts, we may have to consider renaming the mushroom Swiss Cheese.

Additional Notes