Sorry i do not have much time at the moment. To answer part of your question, there is no config.js because everything can be modified from the editor config tab within the Editor Options (a link to the options page is bellow the editor, when logged in as host user).
But at the moment what you are trying to do will not work, because you can only specify an local file for the contentcss setting but no url. This would be an option i have to add.
But at the moment what you are trying to do will not work, because you can only specify an local file for the contentcss setting but no url. This would be an option i have to add.