A (pseudo-)scientific question - has Ravi (or Liv!) researched the possibility that having been a zombie and recovered, Major is now A) immune and B) a source for a vaccine?
In fact, I'm predicting now that A is true but not B. At some point, Blaine's father, or possibly Boss, will try to re-infect Blaine and fail. Ravi will determine that Blaine and Major are both now immune to the Zombie virus. This will leave Liv's personality changes as the ultimate reason that they break up.