What hurts a narcissist is not giving them the attention they need and damaging their image of themselves. If my image of myself is that I am handsome and desireable and my partner gives attention to another guy and ignores me ... look out! Bad **** happens!!
I think a narcissist can change but they must come to understand that they have a problem and seek out why. Until this happens the images and ideas we create in our minds are so strong, they are impossible defences to get around.
In my case after my wife stopped giving me the attention I needed I moved out, it took another four years being apart and then her having a heart attack, almost dieing and then after all that me being a horrible person to her ... for me to final ask myself what is wrong with me? Once I asked that question the understanding came very quickly. Change is not as easy.
I think as long as you give the narc what they desire there is no reason for change. You have to do what is right for you, don't feed the dream, just don't play their game. Eventually they may come to see themselves more clearly. If my story tells anything, it takes a long time and it's not easy ... sorry!
Also you must always keep yourself safe and please don't put up with abusive behaviour, it does not help them, and you don't deserve it!
There is a lot of info on the internet for Narcissist Abuse Survivors, there are chat groups and stuff that I think can be very helpful and supportive for you. Best of luck!