The thing that strikes me in all this, is that he has not mentioned changing a thing about himself, just moving in with you, and you pretending the last few years didn't happen.
I have to say, if you read the NPD boards much, you will see that they (Ns) tend to draw you back in again and again, and then spit you out again after that as well. It is mostly about their convenience.
I posted on my thread recently about how my H's OW1, my former friend, committed suicide a couple of weeks ago.
But they say that Ns rarely commit suicide, though they do make quite a drama of "trying". This is not definitive though. Who knows what your ex is, inspite of displaying so many narcissistic traits.
((((((((((((((((((((((hugs to you Mea)))))))))))))))))))
and stay strong.
Livnlearn
"The unexamined life is not worth living" - Socrates