Hey @jvarkevisser!
Glad that it worked for you! 
Yes it is possible! for now I have deleted the cauchy stress solution field. You can again create a new by going in to Solution fields under Result Control and add a new solution field. You have to create a new run and finish it to get the desired solution field results.
Yes you can do that but so far not on the online post-processor. Local Paraview can be used to do so. Please follow this post for post-processing. All you need to do is to apply the Extract Block filter and only extract the volume you need.
It shouldn’t be a surprising point! it’s due to the fact that both of our upper and lower bodies are completely rigid. For the lower one whole volume is constrained in all directions, whereas for the upper one whole volume is constrained in 2 directions. If you want to make them non-rigid, you have to refine a bit the internal faces of the two plates and then only constrain the upper faces with the same boundary conditions. You will then be able to see the stresses in plates also. But also keep in mind that doing so will increase the computation overhead and may not converge as easily as it did before.
Hope this helps. If you have any question/s, feel free to ask.
Best,
Ahmed