Thank you for playing our game, here's some answers to your observations:
1. There's actually a refraction that surrounds the enemies even when they're invisible, you'll notice how the environment gets distorted in some areas, that's where an enemy is located.
2. Lol, the gun is supposed to be saved for the Boss, since it's the most aggressive enemy in the game and the gun is your safe way to dispose of it.
3. Yeah, the map is certainly too big, but the roads and the Campfires are a good way to not get lost, also when resting at a Campfire the player will always face at a fixed direction, that's the route you should follow to get to the Boss location.