He’s sought her out this time, made a decision knowing what the most likely outcome will be so there shouldn’t be as much regret or him blaming her as there might have been had they had sex after the confession.
Yes, and I think there’s a bit more to it. I rewatched the whole series yesterday and his infatuation with her is overt right from the moment they meet. (The stammering and losing his train of thought when he sees her at the church is such a giveaway.) She does chase him, but he knows exactly what she’s looking for and why because he wants it too. He admits that on the bench sure the “foxes” scene.
Watching the final scenes in episode 5 take on a slightly different tone is you watch them knowing that he’s been balancing his attraction to her against his conviction that his faith has rescued him from a previously bad life. When he tells her he can’t sleep with her because he’ll fall in love with her, he’s actually confessing that he IS in love with her and consummation means choosing her over his decision to find safety in his faith. Which he does, very deliberately.
My fear goes back to the therapist’s line about how shagging the priest won’t make FB feel as powerful as she thinks it will. I don’t think he has a virgin/whore complex, but it’s entirely possible she does - and that’s how her family would view her.