1-Visualizations will only work while on MP3/Music mode.
2-You'll have to use the "Other Visualization" option in RRConfig and define the new area of placement for the vis plugin in each screen you wish it to run in.
3-You can test the results of this work on a single monitor. Just run RR on a 1280x1024 res for instance, and have the vis plugin display at position 800 (RR will be to the left of it).
Still, the best thing for you would actually be to not embed the VIS at all and just position it to start/stop at the right place on the 2nd screen, like x=800, y=0 (on it's own).
Although I think your biggest problem may be when it comes to setting up the 2nd screen as an extended desktop -- an option found in most cards with video Out, but most small LCD screens I've tested are not detected by the cards (unless you plug a Circuit/VCR in between for instance).