Has Levaquin, or any fluoroquinolone med, ever been used as a chemotherapy drug?

Yes, you're correct! Here's a link for you: http://www.collective-evolution.com/2014/10/15/fda-allows-chemo-drugs-prescribed-antibiotics/
No, but added yes! Chemotherapy many times gives Neutropenia, ( low White blood cells) So in many institutions Flouroquinolones are added if fever develops in patients with neutropenia, Many added to Anti-Pseudomonas Penicillin and/or Cephalosporin Antibiotics.