Adding the cx_Oracle package to change-configuration.yaml requires you to do a build and apply to get the change into the sas-pyconfig cronjob definition.
If you want to avoid a build and apply you can use OpenLens or some other means to edit the sas-pyconfig-parameters configmap to add the cx_Oracle package to the default_py.pip_install_packages parameter that defines the current sas-pyconfig job.
I expect this will take care of the problem.
If that doesn't help...
1. I cannot see the resources: from your kustomization.yaml but make sure you have a reference to - site-config/sas-open-source-config/python in there.
3. The sas-pyconfig job takes quite a while to complete so check the log from your sas-pyconfig-adhoc job just to make sure it completed and did not have any errors.
I was able to successfully add cx_Oracle to a test deployment following the blog steps so I think you are really close.