You need to do this in the BT init sketch, you only need to do this once!
Serial.println("SET CONTROL ESCAPE 43 00 0");
Normally the arduino starts in data mode to change to command mode you need to use this code;
After that you can preform all the commands discribed in the manual from the WT11.
The serial connection between the ArduinoBT and the computer or other devices is used by the WT11 and the arduino. So you can't send data back to a computer when you are in command mode because the WT11 is using it to send the data to the Arduino. But you can save the data in a string or in the EEPROM.
When you are done in command mode you switch back to data mode by using the same code for switching to command mode. After that you can restore your connection with the PC and send the data from the string or from the EEPROM to the computer.
For as far as I know the ArduinoBT will not be rendered useless even if you make a mistake in the timing. When you reset the board it will work again and then you can change another timing. The only thing that you need to watch out for s not changing other things in the BT init sketch than mentioned above. Making a backup from the init sketch before you change everyting would be a good idea.