If I log on from a different IP Address such as from school or at my cousins house, will the server think I'm sharing? I don't want to get me or my cousins banned.
No but don't vote from other places wifi, if you are regularly playing at each others homes you might need to sign up for the whitelist.
I occasionally vote from my phone or my school's computer so I can keep up with the 24hr clock. Should I stop doing that?
I would much rather vote using your phone than school computer, it could be a problem if others play from the same location, voting using phone 3g/4g would avoid any potential problems.