The first I do not know.
Second. The GFLOPS/s reported by Nvidia is your:
SP Clock Rate * #SP * #Floating point operations pr cc for each SP
In your case Shader Clock is 1.625 GHz. It has 64 SP. Each SP can do a MAD instruction which is 2 flops and the SFU associated with each SP can do 1 multiply - if they not busy. Giving you a peak GFLOP/s at:
1.625 * 64 * 3 = 312 GFLOP/s
A more reasonable estimate is not counting the SFU and just issuing 1 instruction pr cc. But that’s on the low side. This doesn’t count for double precision floating point operations.