Very minimal annotations this time out. (Although the "two weeks" comment was helpful in updating the FINAL CRISIS timeline.)
Before he was Black Lightning, Jefferson Pierce was an Olympic decathlete, and over the course of this story we see him doing a few decathlon-type things--this, I suppose, would be one of the sprinting events...
...and this would be the hurdles.
As Evie points out, the "that's right" is a very blaxploitation gesture.
Jefferson's two daughters are Anissa (Thunder of the Outsiders) and Jennifer (Lightning of the JSA).
Here he is throwing the discus.
Jefferson was also a high school teacher for a while, and later the U.S. Secretary of Education under the Lex Luthor administration.
Who was the colleague he was trying to rescue? From FC #4, it looks like there were already a bunch of his colleagues at the Hall of Justice. (But he might not have known that; information-transmission is at a premium, obviously.) ETA: commenter Smurph indicates that it was probably Oracle.
The origin of "shoulder to the wheel" appears to be Aesop's fable of Hercules and the wagoner.
Suicide Slum was first named in STAR SPANGLED COMICS #7, although Kirby relocated it from NYC to Metropolis in JIMMY OLSEN #133. (Its official name is Hobb's Bay.)
"I learned it by watching you!"
Thunder, created by Judd Winick and Tom Raney, first appeared in 2003's OUTSIDERS #1. She seems to have gotten better after her brain injuries in recent issues of OUTSIDERS.
Incidentally, there's a real-world Omega Initiative!
Not exactly subtle to be burning a copy of Darwin... but this issue is not about subtlety. I'm wondering what the "S" painted on the window and the wall means, as opposed to the Justifier "J" we see in FINAL CRISIS #4 itself. [ETA: Several commenters have pointed out that it stands for "scapegoat"--see the Kirby image about three-quarters of the way down this page.]
Andrew Hickey points out that what Jefferson is saying echoes Gregory Bar Hebraeus's probably apocryphal account of Caliph Omar's order to burn the books of the Library of Alexandria: "they will either contradict the Koran, in which case they are heresy, or they will agree with it, so they are superfluous."