In addition to what @dc42 said, timer 1 on the X5 family is designed for doing what you are trying to do. It has lots more prescaler options and the base clock can be changed to 64 MHz (or 32 MHz).
I suggest swapping the timers so timer 1 is available to use as you please...
Bear in mind, that changes the core. All your ATtinyX5 applications are affected.