Hi rosserluke,
1.) You can't listen to ATC via RadarBox. RadarBox is only for receieving ADS-B signals from aircraft. If you want ATC best to get a scanner as well.
2.) Yes, you can choose to switch off network flights (its free in the first year anyway)
3.) Yes you will only see local flights. Range is dependant on your local setup as it depends whether you have lots of hills in your way and where your antenna is placed. Having said that even with bad setups you should be able to get at least 30 miles direction. Give us more information about your location and we can give you a better answer to that.
Hope that helps.