Maybe this is a Goldilocks thing. I've tried getting angry at this behavior for years... doesn't work. When I first started DBing, I simply ignored it and refused to be baited, and it went away, but the underlying disrespect or resentment or whatever fueled it didn't go away. Now that it is back, I don't feel I can authentically just ignore it in a STFU/ eating my $hit sandwich kind of way. It makes ME too resentful and I don't want to feel like that.
It feels like we've gone through very similar processes, May. I don't think I'm at all ahead of you, and in many ways our situations are extremely different. But I think what we have in common is that we have struggled to respond to a H's sarcasm, contempt, entitlement and resentment in healthy ways.
I do think that STFU and validation are good when all else is failing. But if you are choosing a marriage, and you are choosing to be connection with someone who says they want to be in connection with you, then there's room for more. And that 'more' is assertive communication. I'm not sure that is covered in the 'how to respond right after BD rules' that are so useful to us all at the start. But I do think those rules help us develop self respect, self control, self-soothing mechanisms, boundaries and a willingness to take responsibility. From that ground work (that your H has not done yet) we can speak something like the truth.
For me, I realised a lot of my anger was coming from the fact that I had allowed my H's anger to silence me. Once I decided that I would not be silenced, and he could either leave me, control himself, or hear me respond in an honest way to his childishness and I knew I would be perfectly okay with whatever he chose to do, but the only thing I would be okay with from myself was speaking it out loud, things changed for me.
I don't have a good marriage. I think my H is unhappier in the marriage than I am, because he'd prefer the fawning punch bag he used to have. I am unhappy at times, at other times I see improvement. What is consistent is that I feel better about myself, and feel like I am in a better place to make good decisions from.
I am excited for you, May. I think you stating what is true for you calmly and consistently is going to help you find your best way forward. I hope your H is enough of an adult to do the groundwork so he can find his own truth - but who cares - you are on your way.