I really don't see anything wrong with his going to bed a little earlier, talking quietly to himself, and falling asleep. In fact, that sounds healthy. It seems like he's soothing himself from a tiring day, and that sounds restful. Just because he's not truly asleep during that time doesn't mean he's not getting valuable rest. As long as there are no electronics or books, just lying in bed and calming down with quiet talk seems worthwhile. I wouldn't worry about that.
And I agree about the snack. He may need a little more protein. What does he eat for breakfast? And lunch at school? It may be that he's more in need of a piece of cheese or yogurt or some peanut butter when those grumpy times pop up.