I know things really started to move in my marriage with my H's sarcasm and meanness and contempt when I started with the truth darts.
Previously, when he'd acted like that, I'd either been very upset and tearful, got angry, or tried to logic him out of his horrible state. All of that was about changing him.
When I got out of the way and left him to be mean to an empty room, that helped ME and it got me into a state where I could start to do things that helped the relationship. I had a LONG time where I was STFU and I think it did achieve some necessary peace and stability and allowed me the space to heal - but part of my healing was to get angry about how I'd been treated and what I had chosen to allow, and also to see the truth. And for me, healing action is about speaking the truth.
When he is mean or sarcastic with me these days, I say 'if you're angry about something, you can tell me directly and honestly like an adult and I will hear you out. I will not be in the room for your childish sarcasm and petty remarks. I will not allow you to act out like that around me,' or some version of that. I name what is happening, what I want, and what I am now going to do. Then I leave the room and leave him to deal with his own anger.
And I do think sarcasm is a very passive aggressive and childish way of expressing resentment, anger and contempt. It's laziness - letting off steam by lashing out rather than looking inside, seeing what is wrong and expressing it clearly and assertively. I think he probably does want lots of cookies for telling you - again - that he's willing not to contact his mistress, and he's having little sulky temper tantrums now and again to let you know how resentful and deprived he feels. He is an extremely entitled man. It is very very very good that you named it, said it aloud, and called him on it.
