Just wait until your monowiper fails and you take that apart.

You've got this one solved...for the most part. Now you need to make sure you have the plunger protruding the correct amount. The flapper should NOT contact the plunger while the car is idling. It's a feel thing.

p.s. As another poster mentioned, B12 is aggressive. I only soak all metal pieces, never pieces with plastics or rubber or paint, etc. The carb cleaner comes with a little tube to direct the flow. That is usually enough to spot clean the gunk that can't wipe or "brake clean" off.