I was raised by a narcissist, and have a personality disordered husband (and I always thought that Freudian stuff was for the birds
)
I suspected personality disorder in my husband for a very long time, and had been told, fairly informally (as you were), that there were traits evident. I knew of his family history (in fact, I've known him since I was 15, so I witnessed a lot of what went on in his household growing up), and it was long obvious that his needs surpassed mine---and to me, it was obvious why. (He was horrendously exploited and abused as a child. His needs were never met---and he was belittled, berated, and scapegoated within his family.)
And he saw no problem whatsoever--for years and years. (Even now, post-diagnosis, he has a frightening lack of insight into how his behavior affects others.)
After our last D-day, I insisted on a diagnosis based on objective testing interpreted by a behaviorist and psychiatrist very skilled in diagnosing personality disorder. He had been tremendously resistant--for years. Destructively, angrily resistant. This time, he recognized, albeit briefly, that there were huge problems with his behavior; this motivated him to accept the testing.
The testing told me exactly what I already knew. Seriously, he handed me the psych report and said, "You were right." (There has never been a time--ever--when I least wanted to be right.)
But test results didn't really clarify my life path for me. Will he get better? Maybe, a little--if he's really motivated. Can he learn to interact more appropriately? Maybe, a little, if he's really motivated. Can he learn to care, and to have empathy and feel remorse? A lot iffier. Behaviors can be learned--feelings are trickier. Can our marriage improve? Yes--but here's how: if I accept him just the way he is and reframe all of my expectations to fit reality. Can I do that? At this point, I really don't think so.
Most people with personality disorders really don't see the problem with themselves---it's always someone else. And even if they do have glimpses of clarity--which many do---it does not tend to translate into long-term behavioral changes. If you don't really see a problem, you just don't have a heck of a lot of motivation to make big changes to improve a situation you don't think is that bad to begin with.
Aside from the general difficulty in getting a diagnosis (getting a PD individual tested can be extraordinarily tricky), you have to consider what you will do with the information.
For me, knowing what I am living with accomplished two things. First, it helped undo a couple of decades of gaslighting. It reframed my experiences. (On the flip side, it has required me to very painfully reframe all that I believed to be true, as well as examine my hopes and dreams and expectations--none of which will now come true.)
Knowing has also given me important information for decision-making. The decisions have not made themselves--it's still very, very painful. But as things unfold, and months go by post D-day, and I see the very limited way in which he is able to respond to my pain...well, I can see how my needs are going to be met. And this gives me a glimpse of my future---which helps guide my decision-making.
I'm just sharing this because I know how difficult personality disorders are to cope with, as a spouse. But I think it's really important that someone very qualified make the assessment, using accepted tools rather than general impressions.
I also think it's really important to find a behaviorist very skilled in treating the personality disordered; I think your MC's advice about feeding your husband's narcissistic supply as a means of eventually having your needs met (a) asks you to make unreasonable changes, and (b) might be--if he is genuinely narcissistic--really, really misguided. Why? Because that's not how it works. If he really has NPD, feeding into it will NOT help meet YOUR needs. It will feed the monster.
You can't fill his black hole--you just can't. And trying can be harmful to you--cause you to sublimate your own needs--and have really undesirable results.
I have found a great deal of support and good, solid information at www.outofthefog.net---it is a site devoted to those living with individuals (parents, sibs, spouses, etc) with personality disorders.