[gray pierce]

I just replayed and finished Overclocked and looking back I don't get why I didn't get it the first time round as David actually spells it out for you himself

"I'm still here. My eyes see. My ears hear. My head thinks. The other is dead"

In other words he's in a coma and is imagining getting back together with his wife and the police ariving to close the place down(while in reality they probably never got away from Fort Tilden)

Also to further this statement, his last lines are: "I'm alone. At last." while at the ending it is obvious he is not alone at all. I think these lines symbolize his concience being dieing and his mind slipping into a dream state.

This is indeed a sad ending but I think the most likely solution

Anyway, no matter how you look at it: brilliant game!