fixed - finally
I finally got off my lazy behind and ordered the relay from FastLane (the correct part number, btw is 201 821 02 47). Took me less than 10 min to replace the relay and now my wiper works like a charm.
To think that the dealer was going to charge me 800 bucks. The part from FastLane cost me only 40 some bucks. (And the order came right on time)