depending on the brightness of the projector you might be able to just send the projector black and it wont be to visible. some projectors have a "shutter" or "no show" mode, these often still leave a little bit of light. you could pull the plug, but then you would need to go thought the start up cycle every time you need it in the show. just out of curiosity, why cant you use a physical
douser to block the light?
for the software, what are you wanting the software to do. are you looking for play back options, or building the actual video file.
for control Ive used light weight software such as power point, to Que lab (mac only) to tricaster studio for show control software.
to build the file, i would suggest adobe after effects.