1. 470 ohms empirically determined to give best distortion performance if memory serves me.
2. Best guess is 1/8W, maybe less. The voltage swing will be less than rail-to-rail p-p over 470 ohms so that's 9.6 mW worst-case for a 3V supply.
3. It's a CMOS logic output (per DS Figure 20). I don't think impedance matching really matters here, just buffer and low-pass filter the signal.
10 years later, have a follow up question to the above!
Am using divout and do indeed need to band pass filter the signal due to some spurs coming from intermodulation between the reference clock and the VCO, so knowing the actual output impedance of divout would be useful for optimising the filter design. Do you have an output impedance figure for the CMOS output buffer on this pin? It's presumably > 1kR, but is it closer to 10kR or higher? Many thanks, Dave