Two states cpu-less PWM generation
You basically need to output either pulses of 1ms or 2ms in a 20ms grid. Your 0,1% accuracy calls for a crystal oscillator.

Use a 1MHz crystal, divide the clock by 1000 using a cascade of three CD4017 counters. You have a 1ms clock now. Use another CD4017 for the "1ms, zero" and "1ms, one" outputs you need and a single toggle flip-flop for discriminating the first 10ms from the second.

Feed these three inputs and your 1ms/2ms select into combinatorial logic. You are done.