Hi [...],
Sorry to hear about your struggles. You are sort of caught between a rock and a hard place. The Ativan apparently is helping you with the tinnitus, but you risk being on it long-term if you continue.
The good news is that you haven't been on Ativan very long. Usually a taper of 5 - 10% of the current daily dosage is recommended, but in your case, I'd lean towards making it a rapid taper.
Cold turkey may be too abrupt at this point. And I feel that crossing over to Valium would be a prolonging risk. Honestly, I'm not sure what percentage reduction I'd recommend. Maybe 20 - 50%?? Others may want to chime in with their recommendations.. Good luck to you.