It definitely seems to him you’re just napping and he’s carrying the load.

Yes, this is definitely the case. OP needs to better communicate with him what she's going through.

From his perspective at the moment, he is waking up at the crack of dawn, working through the day, coming home, taking care of the kids the rest of the day, eating dinner, going to bed, and then repeating it all the next day.

I don't blame him for feeling like he's doing everything and resenting OP for taking an afternoon nap. OP needs to show him what's going on behind that scene that even allows him to do this.

He kinds thinks that he's magically able to sleep through the night or go to work without worrying about the kids. But that stuff doesn't happen by accident. It's only possible because OP is making sacrifices.