They are very good at apologising aren't they. He might, in the moment he is saying them, think he believes sincerely in his apologies.
But if you continue along your path now, he will eventually change his tune completely and start trashing you to other people.
You could just engage with him politely, briefly, and ask him to actually WRITE to you laying out what he admits he has done in the past and to write down his apologies. I have three letters from my H in which he admits everything - that he drove me mad with his silences, his emotionlessness, his inability to engage with me or feel empathy, his total lack of friends and his cruel behaviour. He apologises profusely for being hurtful, poisonous etc, and says lots of wonderful things about me before closing with the line that the only thing for him to do is 'disappear' which sounds like a suicide threat.
The letters may one day be useful - perhaps to show my ds - because since abandoning us he has, of course, re-written history totally: he now tells people that I was drunk every night, had mental health issues and a terrible rage, and that he was just an ordinary, 'peaceable chap' caught in a 'typhoon' which he couldn't handle.
That's what they do: they will trash you to their friends, slander you, lie lie and lie and treat you with contempt. It's pathetic but horrid too.
Your reaction to his pleading is normal and human - comnpassionate! Of course you think he may have 'seen the light' and of course you want some moral justice and to think he can finally see what a shit he has been and how you have been a bloody saint to stay with him for so long. But if he is indeed NPD it is all just words and nonsense. Bluffing. Smoke and mirrors. He is playing to your human gift of forgiveness which, god knows, you must have in spades to have endured all that you have. He knows which buttons to press. He knows he is drinking in the last chance saloon and is pulling out all the stops to reel you back in once more.
They are breathtakingly manipulative. He is still blaming you for his treatment of you. Classic. So what exactly is he sorry for? yes he is sorry for himself alone really. But he knows that normal humans apologise to the other person when they have fucked up so he is doing what he knows is 'expected,' to get his way.
Well it's your way now. And you know that you cannot go back. Ignore his wheedling attempts, (though as I say, you could ask, if he next calls...'I want you to write it all down in a letter to me and I shall read it and think about it and come back to you') and for once in your life reserve any sympathy or sorrow or compassion you have for your DC. THEY need your reserves of these, not this man.
Keep going. Keep smiling. You will go through grief and anger and other normal emotions at your marriage finally breaking up. But if he is NPD, you cannot and must not remain with him, for your DC's as well as your own sake.
Grovelling puts him at the centre of the drama whereas you want no more drama and no more him.