The language in the rental contract/waiver/damage provisions will probably hold some weight in resolving this matter one way or the other.

Don't think a suit is necessary (at this point) for the $6k charged to AMEX. I would definitely dispute it in writing - it can be considered a fraudulent charge.

I am not willing to send an e-mail to Island Rentals, but will remember not to use them when I return to the island.

Hope it all works out.