Regarding Best Practices, I don't think there are any standard ones. Your idea is perfectly fine. Move them into another stream or engagement program altogether and do some A/B testing to see what works best for that group of persons.
For your second question, you can use Email is Delivered as a trigger or better yet, a recurring batch campaign with Was Sent Email or Member of Engagement Program & Exhausted that runs after your cast. You'll need to play w/ the timing of the recurring campaign but this is the best way IMO.