1. Nothing can safely repartition ntfs. You should take backups of everything you don't want to lose, then try qtparted with knoppix which sometimes works, sometimes borks.
2. Yes, but for better performance you should compile a kernel or install kernel-source/headers for knoppix. Haven't checked if they're actually available. http://kanotix.com installs nvidia with a simple script.
3. Used to recommend mandrake, called mandriva nowadays. All depends on what you want. If you want to dive head in, try slackware. It's quite difficult to begin with but teaches a lot by necessity. Why not debian though, you'll have to learn some commands to configure stuff since a "control centre" a lá mandriva is missing. http://genieos.toluenterprises.com/ (former debianpure) is an easier way to get debian installed and configured. Kanotix has good support though on both irc and forum. Knoppix should not be installed on a hd. If you want to run it from cd, fine, but don't expect an install to be problem free.