I know that it might be very emo of me, but the way I see John finally caving about the otter pops is to maybe overhear Sam tell Dean that he doesn't think that their father loves him. Not in a whiny teen way, but sadly detached.

Your John might not be the touchy feely type, but I could see him slipping the pops into the freezer, just as a little sign that he loves his kid, even if he has to be tough on him. JMHO.