Scarrrryyyy... The sound background and monster noises are really cool! Also the grain filter and limited flashlight radius contribute to the scariness. You really nailed it!
I think having mouse clicks for shooting and for inventory actions is not optimal. There are not that many actions (switching weapons, reloading, swapping batteries) - a key for each of these actions might be enough. As for the weapons: showing in inventory which one is active would help, also making clear how many bullet packs are still left for each weapon. Suggestion: only show the active weapon and its bullet packs. Define one key for switching weapons - no clicks for that.