It's been many years since I have done this but I was taught a trick by an old mechanic for removing ball joints on GM cars that I imagine will work on MB's. Instead of a pickle fork, get a long pry bar(6 feet or so) and apply pressure on the ball joint as if you were just going to pry it out of its fitting. Then strike the outside of the fitting into which the ball joint is pressed with a small sledgehammer. I have found that usually one or two strikes will cause the ball joint to release.