I originally played your game on a Firefox browser, but retested your game on Chrome and it ran smoother! So it could be partially caused by a difference in browsers. In either case, I appreciate the in-depth explanation, as it helps me out when I want to implement enemy controllers in future projects!
I disagree with your camera comment. I think it added a lot of spooky-ness to the game. Only being able to see a small sliver of what's in front of you really increased my fear of the unknown! Again, awesome submission!