In order to justify text in the way a word processor would, one must set 'linebreak' to 'false' and 'parbreak' to 'true'. For every new line, you must use "\n\n" (two newlines, NOT carriage returns as stated in the docs). If you wish to make two new lines in your finished document, "\n\n\n\n" will not work. Instead, you must use "\n\n \n\n".
For every line to be justified, you should append "\n " (new line and a space) to the end of the text. For this to work, 'linebreak' must be 'true'.