Search the Language Editor for the string you want to change, such as "ShoutChat" then replace the proper entry with your preferred name.
I think that these lines may not work for larger screen widths like on a tablet as the sidebar would already load, what browsers/devices are having difficulties?
The most recent shout should be the one at the bottom of the shoutbox.
The mobile dimensions are specifically chosen to industry standards, adjusting things could result in pages not being correctly identified by web crawlers or mobile devices.
"Comment guidelines" is also in the language editor.
