I learned from watching Disney's Aladdin that the person who gives the magic is stronger than the person who gets it.
The queen got the spell from Rumple..soooo...
I gleaned from the last ep that Snow's Dad was Queen's lovahh (yes, I said lovaahh). Not sure if he tried to stop one of the Queen's schemes to kill Snow or got caught in the crossfire or what.
I also think the Queen knows exactly who Emma is, otherwise she wouldn't have gone so far out of her way to adopt Henry. She sent Rumple to AZ?? to get him.