Redirecting Communication/Arguments through Divorce

Hello! My question is about having a conversation with my husband who has narcassistic tendencies. We are also currently in the beginning stages of getting a divorce and have two young children. Communication has never come easily for us and I finally realized that I am worthy of more than being with someone who has been disrespectful, belittling, dismissive, snarky, condescending and rude to me. He can also be a nice guy at other times — Which sounds great but I never know which version of him I am going to get on a given day or time. If I bring up something in a conversation he is immediately dismissive, irritated and places any of the blame on me. I have gotten much better at owning my responsibilities and not internalizing the blame he imposes on me if I feel it doesn’t line up with the truth. However, sometimes these arguments go from a conversation to an argument within seconds and I don’t see it coming. I have tried using the phrase “this is just a sentence, this is just a sentence” to defuse some of the criticism but when it turns into an argument so quickly I get defensive. Do you have any other suggestions how I may respond in a way that serves me during these times? I would love any phrasing or sentences that I can practice when I’m alone so I am prepared. I want to feel empowered and not defensive. I also want to keep things civil for the kids. My ultimate goal is to try and have a healthy co-parenting relationship because I do feel like he is a good father. Please help!