mm43, thank you for extensive and excellent analysis.
Two questions, and perhaps you don't have the answer.
1.) Does your calculated point of impact lie to the west of the westernmost vector of the search grid flown by the Brazilian Air Force on June 1? (That search basically overflew the projected enroute track between INTOL and TASIL with a bit of coverage on either side of the track. On June 2, the search boxes were expanded to the east and not to the west of the track. I realize you may not have the coordinates for the area searched by Brazil on the 1st. Although I understand why the grids were expanded to the east, and then south, if the grids had also been expanded to the west in the immediate days after the crash, the wreckage likely would have been found sooner and closer to the actual impact.
2.) Arslanian in his August 31 conversation with reporters said that the wreckage was in waters 3,000 to 3,500 meters deep. Here is a Wiki profile graph of the area. Eyeballing, 30.5 W is roughly near the vertical bar for the Mirante do Vale building. However, the profile is for 3.5N, not 3.1N, and this is basically an east west profile, with no north-south component. Do you have any bathymetric profile for the bottom near 3.12N, 30.54W?
Notes on the profile here:
File:AF447Cross-Section.jpg - Wikimedia Commons
Added:
Also, the vertical scale of the bathymetric profile is greatly distorted, so the slope between peak and valley may not be so much off-the-cliff as depicted.