Thanks for the video! I'm about to start trying to add a BLTouch to my Duplicator i3 v2.1 (Maker Select variant) and had a question. Were you able to get the probe working using the stock Melzi board or did you upgrade the board to something like RAMPS? I have been reading mixed information about whether it can work on stock board or not. Some people mention it is possible if you disconnect the LCD and use those pins (A4) to control the servo function to raise/lower the probe.
I'm really hoping you may have figured out how to do it with stock board and keep LCD working :)