I think your plant looks healthy and in great shape. So the window facing South is a good place for your plant. If you have this plant for a few years now, you are doing a great job in taking care of this plant! It is wise to repot your plant every 2-3 years or so, and it needs a bigger pot for the size it has now.
For pruning I suggest you wait until (early) spring. During Fall and Winter time most plants have a dormant phase, so pruning the branches and propagate the cuttings are best done at the end of this dormant phase (or do you live in the tropics?). Try to prune off the branches right above (~ 1 cm, or half inch) a node, the new shoots will come from these nodes (armpits between stem and leaf). One rule of thumb is to never cut off more than 1/3 of the plant, however, I think for this rubber tree (which is a strong plant) a little more is tolerated.
For propagation, I would suggest to put the cuttings in a new container with fresh potting soil. The cutting won't need much water yet, because they don't have roots yet. Therefore, if you stick them in the container together with the mother plant (which does have roots) you might overwater the (rootless) cuttings.