Hi Meghan,
This is a great use case, and the features you need are very much aligned with some things we plan to add in future. For now, however, there are limitations.
It is not possible to have recurring actions right now that repeat indefinitely. Check back in a few months though for this one.
For not sending emails to users that have opted out, for now you would need a workaround. What we normally do here is set a flag in user meta (so basically the user’s preference about emails is stored in their profile) and for email actions, we add a condition (see https://automatorplugin.com/knowledge-base/action-filters-conditions/, also a Pro feature), that only runs the action if the user’s meta key for the preference indicates that emails are okay to send. So it doesn’t actually cancel the action entirely, it just doesn’t run it because the condition check tells it not to run.
For now I’ll mark this as closed, but for both elements above, things will get easier in future.