Re the right mouse button, it is set in Android to equate to the Go Back button. I know you can remap remote control buttons or individual keys on a keyboard (both within Android in general, and also XBMC specifically), I'm not sure about mouse clicks, let me see what I can find. Here we are, I'd recommend trying
http://forum.xda-developers.com/showthread.php?t=850464 if you want to prevent right clicking a mouse as being interpreted as go back in Android itself, or the XBMC>Programs>Program Add-ons>Keymap Editor utility if you want to try and only make this change in XBMC itself. No guarantees, I've not tried to do this with either, but those are where I'd start.
Re sleep, if this is within XBMC, check the screensaver settings - System>Settings (or just System, depending on the skin)>Appearance>Screensaver. You can either make the timeout longer, or set the screensaver type to None.
If the display sleeping happens outside of XBMC, just within the normal Android launcher, then I'd check which apps you've installed, as I don't see this behaviour on my X7 outside of XBMC. It might also be worth checking the settings on your TV/monitor to make sure nothing there is causing this.
