After that feat, can you work out when Azoff was manager for individuals as well as the band?

As far as I can tell, he has been manager for Don Henley throughout.
He stopped managing Glenn some time between 1982 and 1984 but they must have remained on good terms, as Azoff was behind Glenn's move to the MCA record label.

In 1994, Azoff was manager for the band and presumably Henley. Felder also seems to have considered Azoff to be his manager at this time. Meanwhile, Glenn and Joe had their own managers (Peter Lopez and David Spero, respectively).

From around 2000 or 2001, Azoff managed everyone (except Felder, I assume). According to Spero, Joe was given the choice of being managed by Azoff or being treated as a sideman. Spero also claims that Azoff never wanted him involved in 1994, but Glenn stood up for him. It seems like there was a lot more going on than the firing of Felder in those 2000/2001 negotiations.