Well, since I can turn the Firewall of through services.msc, there's really no need to do through a command line. I tried it just for kicks, and it does work, although I get a msg about netsh firewall being deprecated.
I just thought that since I am unable to do anything with the left pane of the Firewall page, other than click Advanced Settings, it might be part of a larger problem that is causing to not be able to open iTunes.