Turns out the vast majority of problems with my enemy objects boiled down to either one of two issues:

1) Object maintenance wasn't working properly when they were off-screen. Changing it so they always update even when not visible on the screen solved massive performance issues, which really surprised me.

2) Collisions with walls weren't happening properly because collisions rely on movement. There's no movement occurring when an instance is created in a space. It's only when the object instance tries to move that collision is checked for.

So from here on out, I just need to make sure the enemy can properly work on bashing down a door instead of dying. Once that's done, it's just a matter of inserting sounds, a title screen, a game over screen, and a victory screen. I think that will take care of the rest.