Re: [multiple X screens] can't use the second one (no mouse!)
I had similar problem.
I had an X as mouse cursor on my tv (second display).
Fix for me was
before: first had 16bpp, tv had 15bpp
after: tv switched to 16bpp, so that both need same bpp or that tv needs 16bpp. mouse cursor appeared...
try to use only 800x600 with 16bpp on tv may be it fixes...