As one who once hesitated between a career as a musician and an academic, I find the first part of this chapter deeply moving. I don't know the body of literature about the psychology of performing, but this might well become part of it, if only because it shows how, ideally, a musician will move beyond the performance.
As to the nine years that elapsed: I think the author has given us everything we needed to knoe about what happened that night, at least as far as J's parents are concerned.
As to the man in the bed. Well, be it who he is - I do not necessarily crave a happy end - we yet need to know what happened to Marc, since he was a 'failed gilded thing', too, and, in many ways, more hurt than Julian.