I think Rumple’s given Hook more free will than we’ve seen others give their heart-slaves, but Hook is definitely not doing Rumple’s bidding willingly. And, he’s the Dark One; he may not have to be holding the heart in his hand to use its power. Having it in his possession may be sufficient.
Hook is not blameless for everything (and his recent attempts to blackmail Rumple probably increased Rumple’s desire to toy with/kill him), but the attempted kidnap of Henry and the massacre of the fairies was not his fault. And while obviously Hook does not want what Rumple’s doing to happen, I think on some level he recognizes that there are times in his life when he would’ve done something similar. Like when he tried to kill Black Beard, condemning Eric in the process. You know, like six months ago.
Keeper of Belle's Gold magic, sand dollar, cloaks, purple FTL outfit, spell scroll, library key, copy of Romeo and Juliet, and cry-muffling pillow, Rumple's doll, overcoat, and strength, and The Timeline. My spreadsheet: https://drive.google.com/file/d/0B6r8CySCCWd9R0RUNm4xR3RhMEU/view?usp=sharing