I think Maleficent being referred to as Regina’s sister was a mistake. In the episode The Thing you Love Most Regina called Maleficent her “only friend”.
It’s generally assumed that Bae was sent to our world. If he was sent to another world without magic then the curse sending everyone to our world would have been pointless.
I don’t think Charming died in the pilot but was in the process of dying hence why in Storybrooke he ended up in a coma. Dead people don’t turn up in Storybrooke.
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All magic comes with a price!
Keeper of Felix