In addition to ron's compensation, try this. You already are committed to 0.9 V drop across R1. Use that to turn on an NPN transistor in the classic current source/sink circuit, with the collector tied to the M1 gate and emitter to GND. No matter how fast the opamp is, a single 2N4401 probably is faster.
For adjustability, a 100 ohm trimpot and 100 ohm resistor in series, in parallel with R1.
Pot wiper goes to NPN base.
Collector to M1 gate.
Emitter to GND.
For more speed, add a small capacitor from the top of the trimpot to the wiper. Caution, this might cause a bit of ringing at the turn on transition.
ak