Have you tried the megaphone-in-his-ear approach? Kidding. A better idea is having a calm conversation when you’re not at your wits' end... or dealing with a cranky baby. Don’t attack; instead, let him know how exhausted you are (he might not realize), and explain that it's important for your relationship — as well as his relationship with his baby — that he take on this responsibility.
Remind him that he’s not your helper, he's your partner — meaning he should be just as engaged in raising baby as you are. And yes, that includes changing poopy diapers and getting up for night feedings. If he’s scared of doing it wrong, remind him that you’re new at this too. Once he’s on board, let him do things his way. In other words, stop looking over his shoulder and pointing out mistakes.