It sounds to me as if he wants some attention and has some kind of need that's not being met. I would buy him the clock and say you thought of him when you saw it, and then not make a big deal about it. I would especially buy it if you were not in the habit of doing this type of thing before. Observe what his reaction is.
I wouldn't actually apologize re invitation. Maybe say that you're sorry HE didn't feel he was invited, that he's always welcome at his own home and family. And then drop it after that. Take the attitude that he's always welcome, but you're not sitting around waiting for him, or worrying about him. The unspoken message should be that you're not really worrying about his reactions/feelings right now.
