Thankyou for such an incredibly in depth comment ^_^ I've had someone speak about the key problem before. You don't actually need to restart, but what you do need to do is a little unclear. If you shoot, you can clear your inventory of keys (in doing so you send each key back to the place where it was originally collected) and then you are free to collect the keys in the right order. This mechanics is perhaps a little unclear. Ive made a note, so when I revisit this game, I will look into a way of showing this to the player. I think that will require a crafty bit of level design ... we shall see.
I'm very glad you liked it and if you have any other ideas I'm all ears :D