I think Peeta genuinely cared for Katniss but that he was manipulative and/or that he was a manipulative person. Being in love with a person and/or caring for a person doesn't mean that a manipulative person will stop being a manipulative person and/or that he/she will not manipulate those that he/she cares about. I don't necessarily think he was purposefully manipulative in the sense of consciously deciding to manipulate to get what he wanted, but more so that as a person/character he was manipulative and that he was manipulative with Katniss. Manipulation can consist of deliberate and conscious decisions and actions, but manipulation can also be inherent in who a person is and in how he/she interacts with others. Peeta seemed to be the latter.