A lot of this sounds familiar to me as well, the lack of belonging to any group, always being the clever, precotious child prodigy, spending so much time analysing things in my own head that I develope an ability to empathize with others that lets me get any individual on side, but makes me completely the outsider in any group.
For me however, it is that faculty of self analysis that has been most helpfull. For example, I now understand that my feelings of worthlessness are utterly irrational, and know myself to be my own worst crytic. This is also why, even though I regularly had thoughts of suicide as a teenager and even got to the point of standing over a large cliff, I have had none as an adult because I recognize their origin.
Also, I understand that depression goes in cycles. It has even given me advantages, in my singing, my ability to talk to a crowd, ---- heck even in my academic philosophy.
The one thing perhaps I would suggest is some advice I was recently given by an extremely experienced tenor. He said that a person who simply stands up and sings for themselves, to be admired is simply a karioki singer, is expecting everything and giving nothing to the audience. He said that in order to give something to others and make a real performance, you had to love the music, to appreciate every note and nuance very exactly and then give your own appreciation of that to the audience.
For me, this was a revelation, since I could never understand why i, the quiet one, the one who hates groups and crowds am the person who stands on a stage in front of a large audience and sings. What Niel Jenkins said really seemed accurate though, since my motivation there is not! about others, not about self consciousness, but about giving one of the few good things about myself, my appreciation of music, to others.
this is probably why i get so much out of singing, as it is one of the only times I can show others a positive aspect of myself.
I recently had a spoken viva examination of my thesis, and I noticed exactly the same thing. Because this was work I'd spent the last five years writing, because I believed it, appreciated it, I wanted to give! that understanding to others, I therefore became extremely detailed in my answers, indeed both my examiners said they'd rarely seen someone quite so pationate about their work and so absolutely concentrated on what they were writing. This was not just! because I didn't want my thesis to fail, or that I wanted a doctorate (indeed the doctorate is probably the least important part), or even that after five years of both recovery and! writing a thesis I dam well wanted it to be passed, but because it was something I! had created, something I! had a real love and passion for that I wanted to communicate to others.
it was a surprisingly positive experience, albeit bloody hard work.
So, while I absolutely agree on your assessment of negative narsisism and self absorbtion, there is likely a way that this can become positive and outward instead of being negative and inward, even with everything else.