Fight, I know exactly how you feel. I feel like if I knew he were NPD, as opposed to a bad MLCer or PA, or someone with narcissistic traits just spiraling in the wake of this crisis, then I too could just let go and move on. The reality is that we will never know this. I have seen many counselors. Some believe in MLC, some don't. Some believe in NPD, some don't. All the behaviors I see in NPD I see people describing generally of people in MLC or affairs (lying, cheating, entitlement, abandoning children, unexplained anger toward me, gaslighting, silent treatment, addictions, etc.).
But, what if in this circumstance you had just assumed he would not be helpful and/or compassionate about your S, did not bother to fill him in and/or expect a response, and just taken him to the Dr. when you felt he needed to go. In the end, I think you would have been happier and more in control regardless of what he is.
I just try to have zero expectation of mine. At this point I look at him as a sociological experiment. Someone I observe from afar, but don't allow into my circle or to affect my moods.
My guess is that like me you are a little afraid to just plunge in and move on with your life. As everyone here says, that will either make you a better partner when and if he comes back or will help you weather the storm if he doesn't.
