Lol, the headlight bulb just decided to die at the exact same time I swap the unit. It decided to turn into a 5,6kOhm resistor, leading me in the direction of a bad contact somewhere... Its required to remove the bumper and headlight to switch it anyway... so I'll just replace both now.
Wiring from the unit to the reversing lights is fine.
Schematic for wiring to the reversing switch is inconsistent. The pinning and wire colors do not match between control unit and the switch itself and Renault placed the 3rd pin on a completely unrelated schematic page for maximum confusion.
The reversing switch seems to be dead - no contact between any of the 3 pins.
Gearbox oil will spill out if I remove the switch, so first I want to try a new switch outside of the gearbox and see if the reversing lights work again... and figure out the right spot to put the gearbox oil back in.
This does not explain the AC not working, but I'll tackle the issues one after another.