Goal and options: How can I keep batter from splattering when mixing?
output answer: Place a paper plate on the top of the beaters while you are holding over the bowl.

Goal and options: Cut a loaf of italian bread to insert cheese
output answer: Using a sharp knife, cut halfway through the loaf in one inch squares

Goal and options: What can be used to seal the gumball machine tightly so that no water escapes at all while make a gumball/fish tank?
output answer:
Silicone from a hardware store can be used to adequately seal the globe portion of the gumball machine turning it into a unique gumball/fish tank and prevent water from escaping.