FPGA Mechanical Pressure Limit

Not a guarantee... I'm not Altera. But it's highly unlikely that the device would break under that load, evenly distributed. Assuming it is already on a board, you simply need to have the whole board resting on some compliant, yet firm surface (rubber pad, electrostatically protected). Your worst case scenario would be pressing on the middle of a board that is supported elsewhere (i.e. the corners, edges). The first thing to fail would be the solder itself, or the delamination of the surface copper layers, and it could occur under the FPGA or any other chip, due to the board flexure.