You're trying to set 3 asbackoffLimit of your Job. That means when a Job is created by CronJob, It will retry 3 times if fails. This controls Job, not CronJob
You need to suspend CronJob so than it stop scheduling new Job.
You can do this manually. If you do not want to do this manually, you need to setup a watcher, that will watch your CronJob status, and will update CronJob to suspend if necessary.