You don’t need a separate rule in your .htaccess. Add …
define( 'WP_CONTENT_DIR', 'YOUR_LOCAL_PATH' );
define( 'WP_CONTENT_URL', 'YOUR_PUBLIC_PATH' );
… to your wp-config.php
. Do not write into wp-settings.php
. This file will be overwritten during the next update – never touch a core file.