I'm hoping to do an early morning vatican museum tour (4 hours, meet at 7:15am) on the morning of Celebrity cruise departure. I hear "early morning" vatican tours can sometimes start late. I would have to get back to hotel (15 min away), pick up luggage, ride to Civitavecchia and be on the ship 90 minutes before departure at 5:00. Doable or crazy?? Also, if need be, can I walk out of the tour if the time appears to be running long?
Not sure about the Vatican tour part of the question, but I have taken the train to Civitavecchia and been on many cruises. I think arriving 90 minutes before departure is risky. The reason is my next point, which is when I took the train to Civitavecchia back to our cruise ship it was very late. It is a regional train that makes many stops and it was extremely crowded with people trying to get to the cruise ship. I don't know if that is normal or not but it was my experience. I hope it works out for you!!
You may need to consider a private car transfer.
Even if it gets started at 8:00am you would be done at 12:00. Usually the tours end and you are free to view St. Peter's on your own. Just be packed before you go on your tour. Yes, you can leave a tour early by just handing the guide your headset and explaining you have to leave. You should be fine and you can always take a taxi from your hotel instead of a train.
Allow plenty of time to get out of the Vatican Museums. It's quite a long walk back from the Sistine Chapel. If you have time to go through the connecting door into St. Peter's, I don't know how much of a walk that leaves you. In either case, you'll be outdoors but several blocks from the nearest Metro station. You'll probably want to take a taxi back to your hotel, so scope out the location of the nearest taxi rank ahead of time.
If it’s a Walks of Italy tour (“Pristine Sistine” tour), we ended promptly at 11:15 am as advertised. We finished in St. Peter’s as we were able to take the special passageway from the Sistine Chapel right to St. Peter’s (not possible when the Pope is there on Wednesdays). Enjoy!