No problem at all - I always try to give fair critique to the games I play, and I'm always in awe of the time/dedication it takes to create them, in a lot of ways it's a collaboration between the designer and the consumer at the end of the day. Which can only lead to great things. At least I know now that the door was a glitch, and not my mind playing insidious tricks with me - as someone who used to do QA for a 'leading' game developer there's always going to be bugs in a release, so no problem there, either. If you're a one-person team then all hats off to you, you're doing a terrific job and may you continue with it. Great sense of putting tension/feel/atmospherics in the process. 

With regards to the mouse sensitivity, I'm just one person - see if anyone else feels the same way and take the statistics for your decision, although including it wouldn't hurt ya ;) 

Understand the need for having an alternative button - maybe there could be a poster in the carriage that 'without breaking the fourth wall' ;) lets the user know this without having to look at the menu screen? The more intuitive a feature, the better the result. But maybe I'm just a little dim when it comes to these things, as has already been pointed out to me in the video there was a gun underneath a chair and I didn't see it at all!

They are required yes. Look around, I'm sure that you will find them eventually, they're not really hidden. Minor Spoiler: The head is in a small bedside table in the first car, you will need to pick the lock to get it out. Do you not have the flashlight?