L.W.
It sounds like he just doesn't understand what and why you're doing what you're doing. There's been a lot of good suggestions from others, and I'll add my $0.02. A parenting class that both of you go to together (not because I think you don't know what you're doing) will help provide fodder for discussion. Point him to some websites or books he can go through to understand what needs to be done. Sit down together and talk about if he thinks what you're doing is wrong, or why he's asking all these questions. Then explain what you're doing, and why you're doing it. If he disagrees, then talk through it.
It may not be that you need him to leave you alone, but rather that he may want to be more involved! So let him get involved more if that's what he needs and wants! But if he's one of those dads who doesn't want to be involved and just wants to poke and prod and criticize, then tell him if he's not willing to put his money where his mouth is, he doesn't get to criticize :)