Custom Sharepoint Notification Workflow

I need a custom Sharepoint workflow that runs once a night, and if a task the is due in a number of days, e.g. 7, is not completed it sends out an email reminder to one or more addresses. This will be implemented in Office 365, but eventually we will go online with an internal deployment. I want to trigger an email based on how many days out from the due date any uncompleted tasks are. I've created the attached task list. There are 2 reminder fields. (1 and 2 for first and second reminder in days) I want to trigger an email if a task is not completed by the number of days out in each reminder. This email should include all details of the row in the task list. The first reminder should get sent to the Person in the Assigned To field. The second reminder should go to them as well as the task list owner. No email should go out if the task is completed.