I did some further investigation and found that my DAV should be using NECx2 protocol as described here:
[Link: remotecentral.com]

However, the AX-1400 implementation doesn't allow for a sub-device which is different than the device.

In the end, I did a 'learn' of all the keys of the remote, using RAW mode, and this work-around is adequate for now. Unfortunately, it cuts me off from any discrete codes I discover.

So, the questions remaining:
1. Is there any way to get Sony to fix the firmware?
2. Anyone know of a way to use NECx2 protocol with a subdevice?

Thanks,
Jake