- If you try to index to a missing shard the request will get a 503. A query will work, but only for the available shards and the response will mention this.
- Yep, assuming there is no corruption. It will not recreate the shard unless it has been deleted from the underlying FS as you mention, if it does it'll be an empty shard (obviously).
- Rebalancing should happen pretty quickly and you shouldn't need to alter this.
A few other things; What version are you on? Are you running replicas, and if not why not?
For your last question, see that other thread you opened 