Got it right this time.
Drop @ 18.8mA: 50mV to 1.98V
Drop vs. max. current:
50mV 18.7mA
1.98V 607mA
At 50mV drop, regulation is absent beyond 18.8mA (266R). Doubling forward beta does not bring it up to 20ma. Negative supply to the op-amp would help, but the additional demand of a negative supply seems bad in a low-dropout regulator.
It can't regulate with no load, but 100kΩ (included) is fine so long as op-amp can swing close to +Vin.
Too high slew rate causes problems. Fixed with RC filter.
Relay for simulation only.
Transistor's internal resistances reduced to 10mΩ (except base).
