Is this layer the touch-registrating part of the screen? What is it's function?
> the black film on top of the screen is the Polarizing Layer, it's a thin film that gets put on on top of the touch sensor.
And what are the best approach when 'slicing through' with the wire to avoid this? Have i just tilted the wire downwards against the LCD when cutting..?
>You can remove the polarizing film and add a new one as long as you use the OCA method and have all necessary machinery. Using the LOCA method, you have to be very careful and pull the wire evenly and steadily from left to right without too much force.
Do i pull the wire slightly upwards towards the glass when separating?
You shouldn't have to, but most techs will most likely pull up slightly towards the end, sometimes it goes flying.