Level 2 Password: BQVQK
Level 3 Password: WNLRM
Level 4 Password: SDGNK
Level 5 Password: CNLML
Level 6 Password: BXGTG
Level 7 Password: QSRVJ
Level 8 Password: TKGJZ
Level 9 Password: LPZCP

  

Thanks to Revolution reader Daniel Schiltz!