I am sorry you are having trouble with your stepper motor driver. How did you determine that the driver was dead? Can you tell me more about your system? In particular, can you link to the product page or datasheet for the stepper motor you are using? How are you supplying motor power? What are you using to control the stepper motor? What, if anything, changed in your system between when the driver was working and when it stopped? Can you send pictures that clearly show the board and its connections, including soldering joints?
As for your question about minimum current, setting too low of a current limit is generally not something that would damage the stepper driver or stepper motor, so long as that current limit is below the maximum amount of current the driver can handle and lower than the rated coil current of the stepper motor.