re: What really happened (spoiler)

Most of what happened to Fenton, Adam would know, and Fenton didn't become a Demon when he killed his father, he became a demon when he became the God's hand serial killer, thats why Adam had to wait 20 years to kill/destroy him.

We think Fenton/Adam's dad is lying about Fenton being a demon, but he's not, the only reason he's not a list is his sins/crimes haven't been commited yet, not sure why killing his Dad isn't considered bad, but maybe its because he actually believed his Dad was crazy and thought he was doing good by killing him, though its obvious Fenton realizes he's a Demon at this point.