Those are interesting points.
I read 'Darwins Black Box' by Behe many years ago, and thought he made good rational arguments about irreducible complexity.
When a genetic mutation occurs, there will be a continuum of effect, from new feature to no effect to death.
Natural selection will only have a certain forcing effect that is weighted to the 'death' end of the scale.
The problem I have with evolution, is the vast majority of any random mutation will be non beneficial and that this process will happen faster than natural selection can remove these defects from the population.