OP Please understand you are in a potentially dangerous situation when leaving. Call Womens Aid for advice on how to do it safely, explaining you think your H is a narc. I think he is ignoring you because he is getting supply elsewhere, I'm sorry. All that stuff about behaving decently since his therapy is just hot air, telling you what you need to hear for him to keep control of you, believing he has changed and the future will be different.
I don't think he wants you to leave at all because that would mean he had lost his control of you. If he is true to type, he will be apoplectic when you do. He could talk down to you disapprovingly like a child or become violent. For someone who always has to be in a step-up position compared to others, he will hate that you are in that position, not him and set out to bring you down by several pegs.
Then Jekyll and Hide will be switching round faster than weathermen on a cuckoo clock, nasty and spiteful one minute then uber understanding the next, persuading you to stay. Be prepared to hear anything to make you stay, whatever he thinks you want to hear that will do the trick.
You don't owe him any consideration for his feelings when you leave. He sure as hell has no consideration for yours. It's all about yours and your DC's self preservation.
Expect character assassination to yours and his family and friends. Expect mind games to get you into trouble with the authorities as in The Archers storyline: police, social services, phone call from your GP regarding report of "your worrying schizophrenic-type symptoms" - I'm not joking - and your GP is not supposed to tell you who reported you, so scary.
Forewarn your family and friends. Ask them to block him on social media. Expect his family to never believe he is the one with the mental disorder, he will likely tell them you are and point to your history of anxiety (caused by him) to prove it. Keep physically away so he can't provoke you then twist things, telling everyone, including the police, possibly, that you attacked him. Go grey rock, contact only about DCs via email when unavoidable, using minimal words, via solicitor for everything else. Do not respond or engage, you know it will only feed his need for supply. Keep contact times with DCs set in stone so he can't dick you around varying them to control you. Consider sweeping technology for bugs, tracking apps, apps giving remote control of PCs. Change passwords. Stash money, get important documents and financial documents and things you cherish out of the house for safe keeping first.
You will come out the other side where the air and your head are clearer. You will get through this. In the meantime, be prepared for his mask to fall and the monster beneath to reveal the extent of his ugliness. I repeat: phone Womens Aid for detailed advice and if necessary, 999.