Judging from the pictures, we know Captain Hook will learn about Belle and her relationship with Rumpelstiltskin. He may try to flirt–he does that very often with women on this show. However, I have yet to see him flirt and be successful. 🙂 He flirted a bit with Snow White and she just glared at him. He flirted with Emma, and not once did she looked amused–only dissmissive and uncomfortable. And she chained him in the end. 😆 Despite how charming he can be, he flirting and teasing does not really seem to work on many–at least on the main characters.
I think if he does flirt with Belle, her reaction may be similar to Snow White and Emma’s–not at all amused or comfortable with him. Captain Hook may tell her what happened with Milah to scare her off a bit–to freak Belle out enough to hurt Rumpelstiltskin. But he spent hundreds of years looking for a way to kill Rumpelstiltskin–I doubt he will let that time go to waste.
As for his favor, I wonder if maybe Rumpelstiltskin will use his deal with Emma to protect Belle. It is either that or Baelfire, since those two people are the only ones that he cares for.