I figured he was Pruitt pretty early on with all the talk about resurrection, and they way he kept saying "Monsignor told me you..." Just seemed like he knew too much about them. I'm guessing they have the young actors in old age makeup cause they'll de-age at some point too.
I have a feeling a lot of people will find this boring because it's slow, but I love a good slow burn horror and I trust Flanagan.