Hi pavelle, welcome!
I've been spared the horrors of having to divorce and co-parent with an N, there are very wise souls here who are already advising you directly, but I know about the pity trap, the helplessness trap, that Ns can set for their sources of supply...
Ns seem to be programmed to take extreme advantage of the human tendency to confuse pity with love. You find yourself feeling sorry for them and mistaking this for a deeper bond, you find yourself wanting to help them and thinking that you might build something lasting on the shared triumph over a problem.
It's bait, only bait. Love includes compassion and pity but it isn't just these things, it includes helping but it isn't just that. If you are the only one to give compassion and empathy, the only helper, it isn't love. In the non-N world even the tiniest infant, or someone who is bedridden and very ill, seems to want to give something back, out of love, and they find a way to give it - coos, smiles, humor, grace, - just 'being love' towards the person who is with them. It's not an obligation, any more than breathing out is an obligation when you've breathed in. It's the other half of the dance.
Ns never breathe out. They cannot dance this dance. They are to be pitied - but from a safe distance. If you can't get to that safe distance [if you must co-parent with them, for instance] pity is a luxury you can't afford. Compassion can help, but it helps best, I think, if you reserve most of it for yourself and those with you who have suffered and N-dured alongside you.
It looks to me like you've pretty much figured all of this out already, but Ns work so hard to confuse and destabilize our perceptions that it never hurts to have someone reaffirming these things.