Okay, I know I said it was the hallway scene that cemented my love for this ship, but I lied. THIS scene is what did it.
The first thing he does when he enters the room is shake Henry’s hand. He recognizes that Henry is the most important person in Regina’s life and he honors that relationship by giving Henry is attention and respect.
And here. He maintains a respectful distance until he is sure that a) Henry is okay with everything - which he obviously is if his enthusiastic “awesome” is any indication, and b) that Regina is still cool with them being together now that they have their memories back. Because he has to believe it’s entirely possible she will want to go back to having nothing to do with him. And it’s probably why he just laughs at her comment about him being more likable in Storybrooke - he knows her well enough to know that’s the closest he’s going to get to an apology for her attitude in the EF.
But mostly I think he is just happy that she has her son back, because before anything else they are both parents and he knows nothing is more important than her relationship with her son. And that’s why I love him, and their relationship, so very much.