All of solidworks functions have predefined accuracy, there is nothing to adjust (with the exception of knit).
You might try a different fuction, though. How about thicken (to create a solid), with merge entities turned off. Then try Combine>Subtract to subtract the new body from the old.
Just something to try.
You might want to try Move Face. Another option would be to offset your surfaces by the .0002" and use a Cut with Surface. You will probably have to Extend or Untrim your surfaces before the Cut.
Really thin cuts like this are not something SW handles well.
I agree, move face might be simpler.
Also, try "replace face"! Although that should be the same thing has move face.