Will this zero-cross detection circuit work?
The rise/fall time of the opto is about 20 microseconds (1000 ohm load) and the time when the rectified voltage is close to zero is maybe 2 degrees of one cycle. At a 20ms period of AC, a couple of degrees is about 100us. It's getting to close to not working is my impression.

Looking at the frequency response graph on page 8, with a collector resistor of 33k you'll be lucky to get 1kHz through this device so I reckon you won't see much of a signal. Even with a 100 ohm load the bandwidth is only going to be about 50kHz and will probably just about work. This would mean a rehash to your optical receiver circuit.

None of this takes into account the reverse recovery time of the bridge rectifier and 1N400x diode or any stray capacitance that might slug the shape of the full-wave rectified signal you hope to have.