Really? "There are no exchanges or refunds for no-shows or unused portions of cruise arrangements obtained with the use of a reward redemption." This sounds like it's NR OBC.
4 questions, 4 answers (without all the self-serving commentary)
1. Yes.
2. No, yes (sort of). Expiration date(s) is shown on the BoA website.
3. Call Captains Club (best) or use the BoA online portal (unpredictable)
4. Thru BoA, not X.
The sentence before entering your information says "Check if your Cruise is Eligible for Upgrade?" In my mind, the response you're receiving is clearly "No". (or maybe "Not Yet")
Email CXC@celebrity.com with the dietary requirements (I got a response within 12 hours). A maître d' is typically located at the entrance to all the DRs, easy to locate. IMO, 8-tops will ensure a slower, longer, less enjoyable meal experience. Ask for adjacent 4-tops.