I think this was after Columbine in 1999 - Eminem and Marilyn Manson, among others, got a lot of the fallout because the media jumped on them as instigators of the two murderers.
During the time this CD was released, there was a huge debate on whether music, video games or movies influence our lives or childrens lives. "Slim" or Eminem was one of the artists under attack for violence and explicits in music.
Most likely saying that his beats shake like waco, since Waco, TX has the Balcones Fault to it's North. It may also be a double entendre, referring also to the Waco incident linking it to Quake the videogame.
In reference to the id Software release "Quake" (1996); the line implies that the person in question has the aptitude greater than or equal to that of the Waco Kid's (Billy the Kid) firing abilities, in that they can quickly approach, defeat, and move on.
because crushing a dog biscuit to snort it might not quite produce the high some drug users are used to, this may instead be a metaphor for selling more records than rapper Milkbone, an individual who somewhat resembles Eminem
N-SYNC was a pop group geared towards entertaining their fans, and basically signing autographs, taking pictures, etc. Eminem states that he is not one of these pop artists and doesn't want anyone to expect him to entertain his fan boys with his attention