JP, I think you need to return this gear and buy new stuff
my main lens is a cron 50 from 1964 and it has a few cleaning marks and scratches , and if I stop down too much to say f8 i see lots of dirt ( I use a clone tool in Lightroom to remove them however) .
That will be dust on your sensor, not in or on the lens.
No dust on the lens elements will show up in a photograph no matter how small an aperture you use on your 50mm Summicron. It is possible that things like water droplets show up if they are on the front of a very wide angle lens because they act as a lens themselves, but even a larger numbers of scratches and dust and dings in the glass will only cause a drop in contrast.
The reason dust on your sensor shows up when you stop down is not because it is being put into focus with the increased DOF. Rather it is because when the lens is wide open the path of the light rays is very wide and light gets
under the dust by coming in at an acute angle to the sensor surface. But as you stop down the light path becomes narrow and instead causes the dust to make a shadow on the sensor. So it is the shadow of the dust you can see, not a photograph of the dust itself.
Try a wet clean of your sensor and you should be able to stop down to f16 and not see any dust in the lens in the photograph. You will at least see that the dust moves around between cleaning proving its not the dust in the lens.
Steve