NonDescriptUser

In most stories, I'd agree, but within this one I think it makes sense. He holds such deep loyalty towards his people that he sacrificed his life for a chance to defeat the "Devourer" towards the beginning, so to return to defeat it or to serve once again would make sense with such a mentality.

First and (arguably) only friend that he's had there for years on end. I would be more confused if he just up and left that place without saying anything. Not saying it's perfect, the relationship developement seems a bit rushed, but the idea is there.

To be fair, not dying to mass force of invading demons is a pretty strong motivator.

Might be wrong, but I believe it was Athena who cursed her. Poseidon raped her in one of Athena's temples, Gods being Gods blame the mortals for no reason, soooo.... the rest is history.

Zeus is Zeus, he's probably trying to figure out a way to get Persephone into bed.

Hmm, yes, 'parts.'