Lots of good questions. Apparently you booked the air through Carnival. This means they have guarenteed your arrival, They will hold the ship for a reasonable time and if they have to sail they will fly you free to the first port and put you up free until the ship arrives. The guarentee may have changed a bit so look it up with Carnival. I was on the Triumph when they delayed departure by 3 hrs waiting for a plane. We didn't care we were having fun and we still arrived at the next port as scheduled. We even gave a big cheer when the party of 30 arrived. They were really grateful.
I understand your concerns and that is partially why I do my own air now, and go a day early. If you do find an earlier flight call the carnival number in your book and tell them, they still try to accomodate guests regardless of your prior arrangments but the guarentee may no longer apply if you change. I hope that Carnival can change it for you. But they are correct, they do it all the time, even with CREW.
Give a big Happy Birthday to Dancer Linda if you see her, Feb 26.