Spilling the milk doesn't add an extra floor. It will only add an extra boss. I found this out taking my characters (I have 4 who have gotten past Big Ben) through and by taking others through. The floor below Meowiarty has two storm minions. If you don't spill the milk that is all you will face, if you spill the milk you will fight them plus Spike the Crusher. There are 15 floors to Big Ben. You can mark and teleport to the Commons for healing, mana, or potion refills. Don't do that to many times or it won't let you back in.