Hi @DLGross,
1. Those Flows created by former employees will keep running until there are problems (like authentication).
2. Under Microsoft Flow Admin Center->Environments->the Proper Environment->Resources->Flows, there would be a list of all the flows created in this environment listed,
3. Yes, those flows could be deleted or adding a new Owner by clicking the Flow in the Flow list mentioned in Step 2.

You may click View Details to manage sharing, or just delete this flow.
Regards,
Michael