Rather than modifying the existing rules granting access you should disable them and create new ones granting the access you want, as the default rules are bootstrapped when the services start, so restarting of services would overwrite your changes.
The ability to actually schedule a job for future execution is driven by create permission on the /scheduler/jobs object URI, but this would not impact the ability to run a job "now" (/jobExecution/jobRequests/<job_request_id>/jobs, /jobExecution/jobs) or create a job (/jobExecution/jobRequests) or flow (/jobFlowScheduling/flows). Updating a flow's schedule is controlled with Update permission on on the flow /jobFlowScheduling/flows/<flow_id>, but pushing that schedule is done with a call to /jobFlowScheduling/flows/<flow_id>/scheduled, and that call would fail if you already blocked permission to /scheduler/jobs, though this could result in the flow having a schedule defined that is not reflected in scheduler.
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Greg Wootton | Principal Systems Technical Support Engineer