I have an ex-husband who I think is ND and he’s said as much himself. If he were a child today it would be identified, but we are middle-aged and the 70’s/80’s were like a different world!
I had no idea at the beginning of our relationship, as he does a good job of talking the talk, but he’s utterly incapable of walking the walk. He became worse as the years passed - as life happened and I had less time/energy to pander to him, with raising DC and my parents being unwell, he withdrew and stopped trying to communicate at all.
Anyhow, I can guarantee you that it’s much more lonely in a terrible marriage than it is actually being on your own. Being lonely within a relationship - where your feelings and needs are ignored every day - is SO bad for you and diminishes you as a human being, in my experience.
I didn’t realise how much of myself I’d squashed down and almost lost, trying to be in a ‘marriage’ with a man who simply wasn’t suitable for or worthy of marriage. Although I felt sadness when I told him to leave, the second feeling was one of huge relief.
You can’t sustain a relationship/marriage with someone who isn’t even trying to make it work. You can’t do all of the running and fix all of the problems. He can’t/won’t talk about his feelings or yours. It’s not about him meeting you halfway, it’s about the fact he isn’t even trying to meet you even 5% of the way. He’s giving you literally nothing to work with.
There comes a point where it no longer matters if his ND means he CAN’T do the things, or if he’s just lazy/selfish/doesn’t care so he WON’T do the things. Because after a while, the end result and the impact on you is the same. And it’s perfectly okay for you to call time in it and say that you can’t live with it - because it’s no way to live.
Ultimately, the marriage has run its course. You’ve run out of steam and can’t do it any more. It might be a sad situation, but it’s not your fault. You’re not kicking a puppy. You’re just saying “enough” to flogging a dead horse of a marriage. He’s an adult, not one of your DC - he’s literally not your responsibility, you’re not responsible for his welfare or happiness. I mean, he certainly hasn’t been bothered about your welfare or happiness for years, has he?
In hindsight, my previous marriage was a shambling zombie of a marriage and I should have taken a baseball bat to it a few years earlier. Hindsight is a great thing, but in the actual thick of it, it’s hard to have so much clarity. But I can say that life is MUCH better on the other side of divorce.
Best of luck with it all.