How to choose the resistances for this current generator?
Which resistor  ratios determine voltage gain for this differential amplifier?

What is output current when diff. Input =0 for any load Connected to any voltage within range?

Next For any differential voltage game whether it is one or 1000 and for any load resistance, how does how to put our affect the current with respect to the input voltage gain?  This ties in comments about what R does.

And lastly how does the noninverting input resistor that normally goes to ground or say Vcc/2 , affect the output of the op amp and does connecting to load to a different Voltage other than 0V affect the current out?