Ok this might be something very... weird but I just saw the movie "The Omen" (the old version not the one from 2006 xD)
Originally, it reminded me as if the Earl is like Christ and that Neah is like the Anti-christ (or the other way arround) The anti-christ/Neah kills of every follower of The Christ/Earl but Karen/Road(?) stabs him and he dies infront of the Earl.
He returns (The Omen 4) inside Delia/Allen....
Actually, now I've wrote this.... Your idea about 14th=Satan sounds much better xD
DGM is such a Gray (no pun intended!) series, that i doubt that even at the very end there will still be no official evil/good side/person. That's kinda the way the world works.
Here, the 14th may or maynot be based on Satan, but i doubt Hoshino will uh......reinact Bible through DGM.....=/
So far, it looks like 14th~Satan to me, but its possible that after we find out WHY he killed everyone, we might end up with 14th = Christ/Jesus/God/whoever