Rumple’s behaviour in this episode is understandable. He’s hurting so he’s lashing out at those around him. His head is in a spin in regards to Belle. Chronologically the Storybrooke scenes take place on the same night as the Outsider. One minute he has Belle, the woman he loves who loves him in return, the next she doesn’t know who he is. He wants her back. He tried magic, his solution to all problems, and it hasn’t worked.He genuinely doesn’t know what to do. Him setting off to find Bae is probably the best thing for him and Belle at the moment. She’s terrified of him and if he stayed in Storybrooke, he wouldn’t be able to keep away from her and the hospital. He’s giving them both some space. His threat to the Charmings, whilst not right, is him ensuring Belle remains safe. He’s not going to be there to protect her so he needs the next best thing. I think when Belle smashed the cup, Rumple realised he wasn’t helping the situation and was only making it worse. He had to leave, and whilst he may have said it was to stop him killing Hook, the real reason is that it hurt too much to be near Belle.
Price of magic. I completely agree with you.
Heros don't get their Happy Ending!