1. Yes, if any segment is cancelled, you may cancel the entire ticket for a full refund.
2. You may call any line you wish, but without an AA #, you will be auto-routed to the general number (same thing in reverse, as an EXP, you may call the general number and you will be routed to the EXP line).
3. Wait. You will spend a lot less time waiting if you wait until a couple of days before your flight. Right now it is a madhouse.