I THINK the reason Rumple might have used REGINA to set up the curse was because Cora went with Henry instead… another rejection of him by a woman. Rumple would not even have to be fond of Cora for him to feel rejected. Using Regina might have been pay back… get Regina and even CORA to enact the curse and pay the price of magic.
I am thinking that Gold is now paying for the magic he used because he lost Belle.