It has only been a couple of hours since my first post, and already I've figured out a better way to handle a bullet system with Godot. Apparently it does not need to implement an object pooling system like other game engines using garbage collection, since there is no GC with Godot.
This greatly simplified my original code.
I also just added a free background music for the game scene, as well as a laser sound effect when firing.
I love seeing everything come together piece by piece.