I don't know about the digital pot, but this function call does not look correct.
if (Serial.peek()=='c')
{
Serial.println("copying EEPROM value to wiper register");
Serial.read(); //read in the 'c'
Serial.read(); //read in the '\n'
// change this
copy_EEPROM_to_wiper;
// to this
copy_EEPROM_to_wiper();
}