He only seemed to know that she made the deal with Rumpelstiltskin and was his caretaker, and that she sacrificed her freedom for her father, family, friends, and village. 🙂 He didn’t know that she loved him–probably why he was surprised when she defended Rumpelstiltskin and refused to help him.
But he never saw Rumpelstiltskin with Belle, so he probably thought she did not mean much to him.
He may target Belle for a bit, but I do feel that he would rather attack Rumpelstiltskin–his whole scheme was to kill him. He called Rumpelstiltskin a demon. He lost his hand and Milah to this man.
Still, Belle is not off the hook (I couldn’t resist 🙂 ). Captain Hook will take enjoyment in ruining their romance. I think the worst thing he could do (so far) would be to tell Belle about Milah.