One thing you left out was SA wants to also hurt Russia.
Russia is their main competition when it comes to delivering oil to Asia. They look at China and India as the real growth markets. Russia is also the competition to Europe for natural gas. Russia supports Syria, where the pipeline from the middle east would need to traverse to get to Europe. Qatar and Saudi Arabia have been supporting the rebel forces in Syria just so they can get the pipeline built. Of course, Iran is their other rival on the natural gas coming out of the gulf and going to Europe. So by pushing the price of oil down not only does it slow the growth in worldwide tracking, it hurts their enemies on multiple fronts. They are fighting for the control of energy sales on a global basis.
Putin is being reduced to fewer and fewer options. In order to maintain his control which has been funded by the extraction industries, he might be forced into confiscatory measures or higher taxes or some combination. Once that happens, confidence from the West will disappear and he will be left with China as a sugar daddy. The Chinese will not roll over; they will get their pound of flesh.
The good news in that scenario is that it is likely to destroy any hopes of a German Russian alliance.