My mind goes right to divorce...

For years, my husband has allowed trivial crap to ruin his whole day. It's toxic. If you look at him the wrong way or say something to him in the wrong voice, he sulks and pouts and is super passive aggressive. He's a gentle dad, but he even lets his sulking affect our son by criticizing the way he's eating his dinner or getting frustrated easily. He's not happy at work. I know he's not. We don't have to make house payments anymore, so all we're paying to live is utilities and yet he still says that since he's the breadwinner, he can't look for another job because what if he has to take a pay cut. I said to look around anyway. He won't bother because he looked at the only other aerospace company in the city TWO YEARS AGO and he doesn't think they'll be able to pay him what he wants (even though he hasn't inquired). I finally am going back to work, and my mind immediately drifts to divorce. I would like nothing more than to permanently get away from his sulking forever. I'd prefer it if he could get rid of it himself and I could keep him, but I'm so over it. He doesn't want to change, he wants to complain and for me to feel sorry for him. Last night at a 4th party, he stepped in dog poop and then he pouted all night because I didn't have enough sympathy for him and didn't come to his rescue. FOR DOG POOP. I was so confused that THIS is what he was allowing to ruin his night. And then today at dinner I asked him what his favorite part of his day was and his response was "I almost got to go home early." It just seems like he's playing such a victim and it's such a marital turn off. My only concern in divorcing him is not being able to see my son every day, especially when I'm in grad school. Any tips/advice/words of encouragement?!