Jumping in here:)

He might even find some "dead" allies down there to help him through.

See, I had that same thought as "galwithglasses" re: the 'human' souls destined for Heaven end up in Purgatory to have the last imperfections expunged before they get there, however I then recalled what Cas said: "every soul here is a monster."
If that's the case, and there are human souls there, they don't appear to be fairing very well:/