12 by 12 square? How high? Use this chart...http://www.wilton.com/cakes/making-cakes/baking-wedding-cake-2-inch-pans.cfm It has a column that shows how much batter is needed for various cakes.
Where to start...is this your first cake baking and decorating? This is really a steep, steep learning curve to order all of this stuff and have it made in two weeks if this is your first time. Do you have a recipe for you...
Make sure your icing is the right consistency, too stiff and you will have to squeeze harder and more likely to shake. And practice makes a huge difference. Do a little every day. When I was going to be doing a scroll...
Wow Gray, you nailed it! Great design and expression on the cow, with no naughty bits or unpleasant parts to eat. Perfect! And the ear tag for the plaque...genious.
Why are you setting it up in the fridge? Is it still in the bowl or already on a cake? If it is still in the bowl and too soft to work with, refrigerating it will only delay the problem as it will soften when it warms up to...