What are narcissistic people looking for in a relationship?

I posted a few weeks ago on Reddit trying to understand if my husband could be a narcissist. It doesn't matter anymore whether he is or not, he is affecting my well-being.

I have observed him and he is miserable too. All responsibilities are a burden on his dainty little mind. He absolutely hates any real participation as a partner. He is good with practical functioning like driving is around, household chores, etc. But he is absent as a partner. The mental load of this marriage lies in my shoulders. So I don't understand why he is angry at me since I mentioned leaving him. He is passive - aggressive and I have started to observe him more closely. His style is to break my confidence slowly and subtly. Like instill doubt, make second-guess my decisions, silent treatment, mean jokes, etc.

So I am trying to understand why is he in this? And what I can do to cut off that supply? What am I giving HIM that is making him stay?