Hello, Miriam.
Your calculation for the maximum step rate for the driver in 1/32 microstepping mode is correct, however the driver should be capable of handling higher step rates in coarser microstepping modes and it seems unlikely the driver will be the first thing to limit your speed. The generation of pulses can be an issue if you are not using a hardware PWM pin on the Raspberry Pi (which should be capable of generating pulses into the MHz range) like Mike mentions.
You should be aware that the torque available from a bipolar stepper motor decreases with rotation speed. This is caused by a limitation of the rate at which the direction of current through the coils in the motor (which are inductors) can be flipped. This forum post has more information about the maximum step rates of motors and increasing the maximum step rate of a system.
-Nathan