Regarding breathing audio: My airline requires mandatory donning of crew oxygen mask when alone in the flight deck. If Germanwings required it too, you would have an excellent breath pattern recording.
Logical fallacy with this: why should a suicidal mass murderer in the moment of his evil deed feel the need to comply with company regulations regarding wearing oxygen masks as a precautionary measure?
But the recorded breathing is explainable, if he was wearing his headset. Which I also don't know why psychologically it would make sense to wear it at this point, but who knows.