Point of no return
One sad aspect of this accident is that, from the moment the FO selected 100ft and locked the door, his career was over, one way or the other. Whatever motivation he had, be it dissatisfaction with his employer, financial difficulties or a spur of the moment impulsive reaction triggered by some remark from the CP would only increase tenfold if he decided to change his mind. The bridge was burnt. Maybe, just maybe, he may have panicked and frozen.
About passenger not being heard in the CVR except for the last moments of the flight, it can maybe be understood. You are in a plane that is supposed to fly over the Alps. If you don't know the area really well: how can you tell whether the plane is descending or flying over gradually higher terrain? Attitude? And of course, what would seem at first to be a stuck doorlock problem would take a little while to be recognised as the CP being locked out. Finally one adds 2+2 and it becomes obvious. The later, the better...