All the points you are listing a typically things a firewall would be doing.
Clearly it does take at least some skills, understanding and time to get ZS to work.
1.Control to sites yes this is possible but if you are looking for an easy solution try
http://www.opendns.com/ I actually use that after my ZS firewall.
2.Same as above you can limit the traffic on firewall or DNS, some thinks like Skype can be a real challenge to prevent the usage.
3. you could maybe to that with ZS but I guess it would not be the ideal tool for that. same thing for details about downloads possible but not easy graphical.
4.yes you can see connections from any of your clients but in most cases you will wonder what it going on there. There is no east answer like this user is playing an online game and downloading porn.
5. This is fairly simple to implement with rules on the firewall. I created 4 rules to limit the internet time of the kids.