That for me is the main stumbling block with OPs story. Take away whether or not he intended to kill Reeva specifically in that moment, I can't see how he can argue away that he didn't intend to kill whoever was in that toilet, surely it's difficult to claim self defence as there was no threat, beyond him hearing some noise, could the locking of a toilet door (which she may have done on hearing him call out, intending to hide) be mistaken for the cocking of a gun ready to fire? (genuine question, I've no idea, never been round guns in my life)
It has been suggested that the shots were angled downwards, or even through the lock and hinges. That could contradict the suggestion he was shooting to kill.
It could probably be argued that if you thought there was an armed invader in your bathroom, that posed a very real threat.