Flat spin / final ACARS message
Given that most people here seem to be accepting and/or claiming that a flat spin occurred shortly after 0210 and the plane hit the water shortly later, I think we may be able to determine the impact time a little closer.
The ACARS cabin rate warning message could be due to bad air data. But if it is, it is bad altitude data. We have no sure indication that there was bad altitude data, only bad airspeed data. On the fairly reasonable assumption that the altitude data was approximately correct, we can then conclude that the cabin rate warning came out about the time the plane was passing thru 8500-8000 feet. Since its a warning rather than a fault it was sent as soon as the condition was recognized, with the usual ACARS transmission delay.
The cabin probably starts descending while the craft is well above 8500 (at a guess, please correct me if I'm wrong), but is I believe limited to a fairly slow descent rate until the plane altitude caches the cabin. At that point the cabin descent rate can exceed the 1800fpm limit and generate the warning. So we might make a ballpark guess that the warning was generated at FL80. Given the descent rate in a flat spin and a time for FL80, one can compute/guess a time for FL0.