I don't have a projector, so can't comment about having to dodge the projection.
The sensor bar does nothing but provide points of IR light for the IR camera in the Wii Remote to pick-up so it can determine where you are pointing it on screen. The cord for the sensor bar is simply providing power for those lights, there is no communication between the sensor bar and the console, so extending it should not be a problem. You could also pick up one of the many wireless sensor bars available to eliminate the wire altogether. These simply run off batteries. The Wii Remotes connect to the console via Bluetooth, so range between the remotes and console is up to 30 feet (bluetooth will work at greater distances depending on interference, but no guarantees over 30 feet).
Do take note that the effective distance between the sensor bar and the Wii Remote is around 12 feet at most (some people have success at a slightly greater distance, but 15 feet seems to be about the maximum, and it may or may not work as smoothly for you at this distance). If you want to use it at greater distances from the screen, then the IR lights at each end of the bar must be further apart. The sensor bar was designed to be used within 10 feet of the screen. You shouldn't have any problems with being off center from the screen. I think the effective angle in a 10 foot radius is up to 60 degrees off center (again you may or may not have problems being at a greater angle).