What do we really *know* about Snape?

[Horst or Rebecca J. Bohner]

No: HPFGUIDX 12844

Hi, folks --

I'm mulling over the possibility of writing a story about Snape, but first I
want to make sure that I've got all my details clear, and that I'm not
getting fact mixed up with rumour and conjecture.  So I'd be interested to
know if anybody's spotted anything about the character (that JKR herself has
revealed, either in the books themselves or in interviews about the books)
that I've missed.  Here's what I've got so far:

Name:  Severus Snape (middle name, if any, unknown)

Age:  Fortyish (since he was a contemporary of James Potter at Hogwarts in
the 70's)

Place of Birth:  unknown

Ethnic Background:  unknown

Family (living or dead):  unknown

Background:  a contemporary of James Potter, Sirius Black and Remus Lupin at
Hogwarts in the 70's.  Deeply jealous and resentful of James, nursed a
grudge against Sirius for nearly getting him killed, hated Lupin for being a
werewolf (and nearly killing him).

Hair:  black, greasy, shoulder-length

Eyes:  cold, fathomless black

Skin:  sallow
Other Physical Features:  tall, thin, hooked nose, clean-shaven, silky
voice, Dark Mark branded on left (?) arm, black cloak

Other Details:
- teaches Potions, but known to covet the Defense Against the Dark Arts
position
- Head of Slytherin House
- first meeting caused a pain in Harry's scar (was this just a reaction to
the then-unrevealed presence of the Dark Mark on Snape's arm, or something
more?)
- "knows an awful lot about the Dark Arts"
- former Death Eater, turned spy against Voldemort
- absolutely trusted by Dumbledore

Any further notable details to add?

Thanks,
--
Rebecca J. Bohner