How long does he usually feed for? If he wakes at 5:45 I would cut that feed in half. So if he feeds for 10 mins, I would only feed for 5 and then put him back down. This way hopefully he will be hungry when you wake him at normal time.
You can then reduce the amount of time every few days, and he will soon realise that is not worth waking for just a few sips, and will end up taking a better feed in the morning, and this should off set the day if that makes sense.