my interpretation:
(1) straightforward-happy-ending
the totem stopped spinning. mission completed. conquered the death/guilt of his wife. happily ever after.
(2) forever in Limbo
the totem spins forever ..trapped in limbo.
(3) n-th level exist
the so-called reality on the aeroplane maybe is still a dream …who can tell what is reality anyway?
(4) the wife is not dead. dicaprio is the sick one.
the wife keep appearing in all of his dreams because he wanted to pull him out from his sick indulgence/obsession in the N-level of dreams. so Dicaprio is the one who can’t believe/perceive what real or fake is instead. not his wife.
impromptuz 