1. Maybe.
2. No, it's not true (and where did you hear this?).
3. Maybe, but not enough to be a concern.
4.
http://macs.about.com/od/application...tilitypart.htm
5. Open each session and use 'Save Copy In' and check the option to copy all media, then select the external drive as the save location.
In your case, 2 500GB partitions should be fine, but if you need 3 go for it.