Cool one, really like everything you're doing with lighting here although it can make navigation a little more challenging, it's great atmosphere.
The enemies are fair, so most of the time it feel like you at least could have defeated them without taking damage, which is great.
The automatic doors to me read like overhead elements that were simply vanishing when you got close, so I didn't realize they were actually doors until I had to fight some cannons on the other side of one.
It would have played smoother with RMB for reload, since you're already using the mouse (and as a gun w/ flashlight, so it would be quite thematic) but R as reload does add some tension, because it forces you to limit your own movement capabilities to reload.
Adding some static overlay features as landmarks would have been nice for navigation. The occasional blood trail or similar leading to nearby doors might have been helpful as well. Making important terminals stand out even more would have been a nice touch also.
Personally, I liked the backtracking for defeating the charging enemies, it works well with the low visibility and door entrances, and the general importance of not backing yourself into a wall/corner.
Fun game =]