I am also assuming you are getting your numbers (12 open seats, etc) from aa.com on the seatchecker feature. That is not indicative of the number of seats *reserved*, it is the number *assigned*. I can make a reservation but if I don't assign a seat then it won't show up. I do suggest being patient. TA's make reservations all the time, some legit and some not, and a cancellation can mean that the inventory reopens. It's what happens when you get F1 A1. Someone cancelled an A reservation in a sold out cabin.

I don't understand what the problem is with SJU. I see D3 so unless you have a party of 4 then you should be able to get the reservation.