Malachite, I had a narcissistic partner. We are now getting divorced. I didn't know narcissist was the name of his personality until fairly recently. For me, knowing his official label really wouldn't have helped things.

Some of the strategies I used to stay in the marriage for 20+ years were:
1) Lay low and always let him have his way and think he is right. He would become intolerable and extra abusive if I ever expressed an opinion he interpreted as different or at odds from his.
2) Seek out friendship and support outside the marriage. Cultivate fulfilling friendships with others and eliminate expectations that he would care about me or be interested in my life. With strong outside friends, I got a lot of my "friendship" needs fulfilled and didn't have to expect this from him. And with no expectations there are no disappointments.

I really wish I had not done these things and left the relationship sooner, but these strategies did allow me to last for a long time. This had some benefit as my girls got to be in a two parent family for quite a few years, which I think had some advantages.

A solution other than divorce? I think if I had been really, really assertive right from the beginning and insisted on therapy early, maybe we might have been able to improve our relationship. But maybe not.