A few things strike me:
o why was he wobbling the yoke so much forwards and backwards, that costs you speed, and knackers your glide efficiency.
o Why wasn't he looking for landing sites (he was up really high, like 2k+ above the mountain top), edit: see comment daughter, decent is measured in feet per minute, unfeathered prop will cause drag, nailing your glide ratio so not 10 minutes glide time before action was needed
o why didn't he set his glide path up properly, to give him time to think?
o why isn't he looking at the checklist for engine failure? (my dad had one in the middle) I suspect he might not have one
o Did he send a distress signal?
o where was the attempt to restart the engine (granted it might not be young enough to have a starter, but he had the height to spin the prop)
Finally, the other thing that gets me, is that the door is open before the engine fails. which either means that he's expecting the failure (checklists are your friend here) so why wasn't he lining up/searching for a river bed for landing?