One more thing. Once you've done what I suggested before, look at your browser for any extensions/add-ons that may have been installed. If you don't recognize it, uninstall it.
Did adwaremedic get rid of the ransomware note?
Unless you install MC..
stay away from the mystery dmg downloads from several sites that say you need to download are downloader to install this program don't its called the mc installer trick mc is a safari extension a hacked one that sends nothing but advertisements to safari so stay away.