Hello all. I'm an otolaryngology: head and neck surgeon. I have some insight into tinnitus as these patients pass through our clinics and operating rooms.
To the OP, I would suggest investing in some custom-molded earphones. Although there is no strict evidence that these reduce long-term hearing damage, there is evidence to suggest that users tend to listen at "lower" volumes secondary to the noise isolation. I'm not sure how conducive these would be to DJ'ing compared to standard circumaural headphones.
Other steps that can be taken include white-noise generators and, in extreme cases, cochlear nerve section which can be an effective surgery. It is incorrect to say that there is no surgery for tinnitus although there is no surgery that can provide 100% success rates. Cutting the cochlear nerve or destruction of the labyrinth (which contains the hearing and balance organs) can be effective. Either surgery makes you completely deaf in that ear and would only be used as a last resort.
The pathophysiology and cause of tinnitus is more complex then pointed out in the posts above and is not completely understood. In some cases, it does appear to be generated by the hair cells whereas, in others, it may be centrally generated (ie in the brainstem or brain).
I hope this helps and feel free to hit me up for advice.