ATtiny45 Timer1 clock misconfiguration
You need to configure timer 1 for CTC, set OCR1C to the max value you want for it, and then set OCR1A to the match value.

TCCR1 |= (
  _BV(CTC1) |   // CTC on OCR1C,
  _BV(CS12)     // System clock/8
); 
OCR1C = 2;      // Clear every 2 periods
OCR1A = 1;      // Match every 1st period


Set other bits as required for the application.