I'm not sure why Jack's compass doesn't work - it's possible that he already has what he wants in having Pearl back, so there's nothing definite for his heart to settle upon any longer (he focused SO much of his energy on getting her back for so long that he eschewed everything else, pretty much). I like to think he's not sure what he wants because he *wants* Will, but can't decide how to go about getting his attention away from the boy's bonny lass. That, and ... well, love is hard. It's not something a wise person immediately jumps into.