Hang on. You went away with work and your parents had the kids? So he had a week with even fewer responsibilities and loved it? Who fucking wouldn't?
He thinks that if he left, his whole life would be like that week. Which is interesting isn't it, because he hasn't factored in being a father in his new life.
As for the poster who said you're not seeing his side of things, well, I can imagine it's hard to see his side of things when he's a dead weight. I think doing the shifts he does suits him down to the ground. He has the excuse of being too tired to do anything except game, golf and go drinking. I could have more sympathy for him if he used that down time to do stuff that contributed to family life. If it wasn't at the stage where he'd asked for a divorce, I'd be calling his bluff. Go on day shifts, be less tired, be more present here, do more of the shitwork, be 'nagged' less, everyone's a winner.
A note on nagging. Like a pp said, no one wants to nag or to be a nag. But, sometimes you're forced into it. The alternative is to give your partner a free pass to live like a teenage boy with no responsibilities but all of the benefits of a home, with a laundry service, meals and all that shite done for him. (I mean, I'd be embarrassed to live like that, wouldn't you?). It's also incredibly disrespectful. He has zero respect for what you are doing. If he did respect you and what you are doing he wouldn't let you run yourself ragged doing it.
I think the hardest thing to understand from your post is what you like about him and why you want to save the marriage? You've got into a position where you're not valued, overworked and disrespected. And you want to stay like it? Why?
Start thinking about what your life could be like. A lot of time has been spent discussing what his life is like and could be like if he changed his shifts. Start centering yourself. There's a much better life out there for you op and I'm betting the very best version of it doesn't actually include him