Calculating correct resistor for an optocoupler
The 680 Ohm is fine. 

The 10-k Ohm resistor on the detector may or may not be fine, depending on what is the speed you want to achieve. Larger resistor values will yield a smaller bandwidth. Smaller resistor values will yield higher speed, but they might increase the low-level voltage when the detector is on.

See figure from the datasheet: