How much AP does it cost to launch the catapult with the calibrated catapult built

Maybe a late answer, but i used the adjustable spanner to open a food crate. so it can be used to open certain heavy objects.

i also used it to help 2 zombies to the next life.

No. However some items that can be used as weapons will add to your homes Defense if left in your chest overnight. This includes heavy objects, such as the Beer Fridge, and some animals, such as the Fat Cat.