This thing about the bedroom door, and the key, and him stating "I felt trapped as my bedroom door was locked " is something which keeps cropping up and which I find really confusing.
The main reason for that being that there is no bedroom door to the bathroom area, so it's not a door between those areas which could've been bothering him because there isn't a door there anyway .. it must've been the door which led straight out from the bedroom to the landing (the bathroom and toilet was within the bedroom area, down a short corridor .. with no doors).
I don't understand a number of things here .. firstly, if you say he carries the key with him, then why not just head directly for the bedroom door (gun in hand for protection), unlock it and then proceed out onto the landing, down the stairs and out of the house .. and get yourself completely out of the way of danger. But why does he even carry the key on him? Why isn't it just in the bedroom door all the time in the first place? (unless he had deliberately locked Reeva in .. i.e. in the whole bedroom/ensuite bathroom area).