Was there ever any idea why he had to do it that way? I mean, why didn’t he simply kill just Pan? And what happened that moment when they disappeared? Did Pan just vanish but Rumple, or his essence preserved by the powers of the Dark One was taken in a bodyless form into the vault in the EF? Or did Rumple eventually kinda absorbed the existence of his father into his life energy?
All good questions and all without answers. There was the idea in the show that Rumple had to die alongside Pan (if I kill him, I die too) but there was never any sort of explanation why the two were tied together.
Many people have said that when Rumple stabbed Pan the dagger went into Rumple as well, which I find really problematic because that dagger is not that long and the human body is very 3-D–meaning there is a lot in between your back and your front half. The dagger isn’t a broadsword. So if that’s the actual reason for why Rumple died alongside Pan, it’s a weak one (for me). Where Pan went…pfft. Your guess is as good as mine. A and E said he was dead and gone. But both vanished.
The Vault of Eternal Goo is…if I say plot device-y is anyone going to hit me? Cause that’s my whole take on it. They needed some magical handwaving thing so they introduced this idea of a secret vault that apparently no one knew about where Dark Ones go (all Dark Ones? Suicidal Dark Ones?) as they “return to the Darkness”
As far as your questions about humanity post-resurrection in Rumple…again, good questions. But I don’t know how much thought A and E give those kinds of questions, especially once the arc is done. Rumple seems to have been resurrected as the Rumple we knew–he’s powerful, he can be controlled, but he’s deeply in love with Belle and committed to his son. He’s still snarky, sarcastic, sly, and ruled by his own desires coupled with love of his family. He has the same amount of power, but now he’s lost his boy and that pushed him to kill Zelena, but then afterwards, he goes right back. It didn’t darken him anymore, as evidenced (I think) by the love he still bears for Belle.