The Sound and Picture buttons are accessed from the 'Customize Buttons' menu on the Harmony software. You can use all of the harmony buttons in each mode, essentially giving you 3X the amount of programmable buttons to use.

Programming Channels on the internet is done by 'Set Up Favorite Channels' and on the software, with 'Settings' 'Favorite Channels'.

As for the Vizio, Call Vizio Customer Care? Other than that, mute would've been my suggestion. And with the X-10, if it is IR, why not try to learn the commands? Can't hurt.