First off, you may want to reconsider the 3D chart. most 3D charts make it hard to compare bars from most data sets. 3d charts are not recommended.
Second, i Dont think you can do a combined chart in 3D. Therefore, you can't add a second bar or even a line. Yet another problem with 3D. In fact, my test doesn't even allow me to create a second YAxis.
I would suggest 2d column chart with a line on the second axis that shows the national average