I'm not sure what seems impossible.
At full step mode, rather than 1/8microstepping, 8000pps/200ppr*60s/min=2400rpm
The heat issue depends on the actual motor requirements, the supply voltage, and the tuning of the driver.
Pololu's cheapest NEMA17 motor has this datasheet:
...which shows it working pretty well up to at least 5000pps in half-step mode with 24V and a constant current driver: (5000/200/2*60=750RPM):
Pololu carries a NEMA11 that gets to 1500RPM with 10Kpps:
What are your stepper specs? What loads are you putting on your stepper, and can you supply higher than 12V to the driver?