Regarding Emma wanting her NYC life back. She had a flood of memories after the potion and they included abandonment from her new family & loved ones. If I had a stranger come to me with, "Luke, I am your father..." I would be meh...where have you been all my life? Sure, she was beginning to bond with them, but I can see how she would choose her old life that might provide safety for her son and sanity for herself.
YMMV, of course.