Is it possible that the dark matter is simply missed variables in the math? I am not a physicist but examples might include: effects of planetary and galaxy rotation, electromagnetic fields, centrifugal force, etc. Or if all of these have been included in the math just let me know.
The primary evidence for dark matter is that calculations show that many galaxies would fly apart instead of rotating, or would not have formed or move as they do, if they did not contain a large amount of unseen matter. Other lines of evidence include observations in gravitational lensing, from the cosmic microwave background, from astronomical observations of the observable universe's current structure, from the formation and evolution of galaxies, from mass location during galactic collisions,and from the motion of galaxies within galaxy clusters.
All the factors you list and more have been taken into account in finding discrepancies from the predictions and necessitating the introduction of dark matter.
In order for the observations to make sense within Newtonian mechanics, which should hold at the level of galaxies and clusters of galaxies it was necessary to introduce the concept of dark matter. The concept also is consistent with the rest of the observations, as listed above, which had a discrepancy.