13.10. Automatic crawling works only when someone browses my site

The plugin uses WP-Cron, which only works when your site is loaded. You can replace/trigger WP-Cron with a Linux CRON job. Linux CRON runs the tasks precisely at the specified time. By making it trigger WP-Cron, you make WP-Cron run precisely as well. You can find several tutorials explaining how to do this. For instance, you can check out this one.