Use script without root
First, the best way to run a cron script as root is to add it to the root user's crontab. EDITOR="vi" ; sudo crontab -u root -e will allow you to edit the root crontab. Once you are doing that you don't need to use `sudo; inside your script.

As for running it every Thursday, check the man page for the crontab table man crontab -s 5 and it will explain all you need to know.