Hi and welcome to the forums!
Now for your questions it is prolly better to post them in the right forum sections, but I give it a shot to answer them:
1. To really do this functions nicely you will need a controller. Even the cheapest controller can do that better than any keyboard. In VDJ Pro (not home) you can map it with VDJ script. I am no expert in VDJ script, but you find great examples at the VDJ homepage and the VDJ wiki. Best look there what is possible.
2. http://www.acapellas4u.co.uk
3. Yes it is. However this is sort of complicated and not really an easy task to do. So nothing I can explain of the bat here.
4. I just leave music organisation to iTunes. I do not care how it does its folders etc. Most DJ software (at least Traktor, VDJ and Serato) do integrate with iTunes nicely, so I also do things like tagging etc. in iTunes.