How to deal with my narcissist ex husband who is the father of my children

Hi there. I am trying to co parent with my ex husband who is a text book narcissist. He lies and doesn’t pay support on time if at all and does all the things he can to try and make me angry and crazy. These are facts and not just thoughts. I have proof of much of it. I have googled life coaches for narcissistic abuse recovery and ALL of them say that you have to cut the narcissist our completely… unless…. you have children. I have three children with him and he was the breadwinner while I was the stay at home mom so he is required by law to send support every month but it doesn’t always happen and it has literally NEVER happened on time. I know that we coach that grown ups can do whatever they want etc… but I am wondering if there are any exceptions when dealing with a person who has a personality disorder and is hell bent on destroying the other person. How do I not take that personally? If I listed the things he has done to me you would not believe them. I don’t know what to do. Even when I do my best to be kind and flexible and accommodating for him he turns around and does the meanest things (lies and false accusations etc that are all provable in court). I thought divorcing him would make this stop but he has actually gotten worse in a lot of ways and I can’t take all the lies and being attacked anymore. I am such a good and honest person – I don’t know how to deal with the manipulations, the gaslighting and the pathological lies. These are all facts… not just thoughts… I have proof.