1. Not sure about the block thing - honestly. I'd swear I knew a couple of years ago, but time is not a friend sometimes
2. I use 'df' or 'df -h' to determine usage and space avail. It tells all the space avail and used on all partitions.
3. If you set up a DNS server, register it with your registrar (godaddy, whatever), then set up a web server on a box; when people type in the domain name, the registrar will point to your DNS server which will point to your web server, which will send them the page.
That's the way the internet works