Helios & TUC
Helios was a tragedy, a classic case of Swiss cheese. i'm still shocked the crew missed the pressure controls set to manual & failed to appreciate the very loud warning. Poor Systems knowledge rears its head again, with a dirty look in Seattle’s (Sorry, South Carolina) direction for using one horn for multiple warnings. -However, the fact everyone was alive highlights the problem -time of useful consciousness .
As far as the OP's father complaining about 'dust' in the masks; that is intentional and part of the engineering to ensure the masks do actually deploy. (it's called French Chalk)
An emergency decent is a well-rehearsed maneuver that (like a TCAS RA) requires positive but not 'panicked' response. Sounds like everything worked as planned; though i'm surprised no one’s raised the 'turn off the airway' chestnut....