1) If you want to install ISPConfig, then yes. Otherwise no. But installing bind will speed up dns lookups on your server so it is recommended in any case even if you dont want to run your own domain names on it.
2) Install ISPConfig as recommended in the tutorial and then proceed with this guide:
3) This is already configured as part of the ftp setup in the guide.
4) The easiest way is to install bind as described in the perfect setup and then install ISPConfig.