On your first pictures the splines don't look like bent but just worn out. Did you try to file the beginning of the shaft side splines a bit sharper (especially the side facing the worn side on transfer case)? I know this would lose a minor bit of effective length but could guide the splines past the egde of the worn part.

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E39 530dA -02 M-Sport Messing metallic
E53 X5 3.0dA -06 Sport Stratus grey
E70 X5 40d -12 M-Sport Space grey