How can breathing be heard on the CVR ?
Perhaps only if he was wearing a mask. If he was wearing a mask then there is a possibility that the gas mixture was off causing strange behaviour.
There were 8 minutes after the descent. The pilot comes back and finds no answer from inside. Well he isn't going to put an axe through the door immediately. He will probably ring a few times and then knock on the door. That's 2 minutes gone.
He is in an unknown and weird situation, so decides to override the door, tries to remember the code and puts it in ... maybe he pressed a wrong digit. Then he has to wait 5 minutes to try it again ??? Is that how the mechanism works. There is not enough time.
Of course we could all jump into the hysteria and call it terrorism, and force all pilots to take a double-dose of prozac before lift off.