i quite agree with you that it's a ridiculous story, but it is consistent with itself.
he had to repent of i suppose letting someone get close enough to him that he would let his secret go. i have no idea. i always thought it was silly. nazirites are odd. but that's where people get a bunch of bizarre ideas about jesus. they think he was a nazirite (one of a vow) instead of a nazarene (one from nazareth).