Wow.. that's a lot of questions.
1) The tenders run consently. You can probably get from the island to the ship in a half hour. Last time we were there we did the Sting Ray and snorkel combo excursion, shopped a bit before hand, went back to the ship, changed and then my daughter and I went back to get our typical tourist items from Hardrock and Harley and we still got back to the ship with plenty of time.
2) Not sure I can answer that because I have not tried them all. We have had several cruise chat members recommend Captain Marvin's.
3) Yes, 9 hours is long enough. Figure 4 hours for the stingrays a couple of hours on the beach andshopping time (the shops are right there where the tenders come go so you don't have to go too far.)
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise, Magic 1/14, Freedom x 2 6/14
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013