Thank you for providing information. I'll go and spend some time on this to learn it better so i can implement it , hopefully
If you don't have experience with opamps, then a much simpler but slightly less accurate solution would be using an LM317L as the current source (in place of R1).
You can get the 50mA using just the LM317L IC and a 25 ohm 1% or better resistor, and calibrate the final result in the firmware.
This will perform much better than that part you suggested earlier.
Note that 25 ohms is not a standard resistor value, so just use a 24.9 ohm, or parallel 3 x 75 or 4 x 100 ohm. Or some other combination like 10 + 15 ohm in series.