I think the obvious question here is why? As in why are you even trying to play around with the front video registry keys when the i910 does not even have a front camera???
If you were trying to reroute the camera feed from the back while enabling the registry values for video conferencing, that's not going to do you any good on the other end of the line if the same hacks have not been applied to the receiving phone. Either way you would not only need to edit the registry... you would have to (most likely) recompile your own version of the dialer and the camera API (for all phones involved). My point is that it does not seem worth the effort when CDMA doesn't even support it. You could very well get it working for all I know... but if CDMA doesn't support the feed, it will all be for not. You wouldn't even be able to test it to make sure it was working properly.