This is what I was thinking. Being Dom doesn't come with superpowers -- you're not automatically good at everything. He's going to be better than you at a lot of things and that's just a fact.
If it bothers him, just tell him that he's finally good for something other than loosening the caps on pickle jars for you. That ought to knock him down a peg.
On the 24/7 thing, that's something you're going to have to work out for yourselves. Do it for a day, a week, a month, whatever and see how it works for both of you. Then maybe you can tweak it a bit and find a happy medium.