Did you do tests to figure out what is causing the head tilt? Also, what antibiodics did you try? A lot of
rabbit bacteria have developed immunities to common antibiodics like Baytril and react well to stronger antiobiodics or even a mixture of two diffrent antibiodics. It can also sometimes take a long course of treatment, a couple of weeks or months depending on the case.
http://www.bio.miami.edu/hare/tilt.html
If he's still eatting and running around, and your vet didn't do sensativity tests and try diffrent antiobiodics, I would do that stuff before considering putting him down. How rabbit savvy is your vet??
Also, I know a number of rabbits with permanat head tilts (their infections have been cured but they head tilt didn't go away) that are living perfectly happy lives.
Good luck! You know your bunny best and I'm sure whatever you decide to do will be in his best interest. I'm sorry you have to deal with this.