Yes, A through D are the only endings. Perhaps the C ending can be explained if we ever make a sequel, either way I think its best left unsaid. Thanks for playing.
So, did the uncle drown himself in order to unite with Sedna and was later ressurected by her, returning as a living corpse?
I will say the uncle is very much alive.
He just becomes a creature similar to Sedna?..
We'd akin him more to a delusional fanboy/henchman.