I was involved with a narc for 2 years - again, not throwing the term around loosely - he is a well known psychologist in his field, and in a more candid moment, he acknowledged himself that he did have a number of narcissistic traits. Eventually I left because I just couldn't cope anymore. I'm indeed the field myself, and KNEW I was being gaslighted, lied to, and cheated on. I KNEW I wasn't going mad, or being stupid, or needy.
You aren't going to get the answers you seek, or an apology, or a return to when the relationship was wonderful, because the person you thought he was, and wanted, never existed. It was just a facade.
I moved on by acknowledging that I had dodged a bullet. That I was lucky to get out of it when I did, and that life could only get better - better anyway that the awful, toxic, demeaning mess of that relationship, where it took every ounce of willpower not to go back in the hope that life would be like the early heady days. I went back a few times before catching myself on.
Put him in a box, and put the box in the past where it belongs.
It does get easier. I met someone new who restored my faith in what it meant to be in a normal, loving, relationship. It took me a while to trust him, but I did.