Strain Gauge with Instrumentation Amplifier question
You've made an error in the amplification.  


  \$G = \dfrac{2 \times R_F + R_G}{R_G}\$


With the values you're using this gives  


  \$G = \dfrac{2 \times 10k\Omega + 25.9k\Omega}{25.9k\Omega} = 1.77\$  


If you want a \$G\$ of 750 you'll have to make \$R_G\$ = 26.7\$\Omega\$, so that


  \$G = \dfrac{2 \times 10k\Omega + 26.7\Omega}{26.7\Omega} = 750\$