Wish I'd seen this earlier There's no need to remover the arm. All you needed to do to get the handle out was to unscrew the wiper motor and rotate it through 90 degrees and you can get the handle unit out whilst still keeping the motor and wiper arm in tact.
Mines was a total nightmare to come off i ended up cutting {VERY CAREFULLY} the nut off. Everything still intact
Be gentle as this ETKA is new to me but I THINK the part number MAY be 3B9 955 985 A - Spray Jet Hopefully someone else with more experience with ETKA will either confirm the number or give you the right 1