Stop cronjob for two hours in a week
Rather than mess with esoteric crontab schedule entries, have your script check for a file and to not do a full run if the file is present. Then, schedule a second script in cron to create that file on Sunday at the time you want the other script to stop, and then another script 2 hours later in cron to remove the file.
That way, you can be flexible about when the main script does and doesn't run by just changing the times of the create/remove scripts.