Smoking like that can also be caused by a blocked air filter . Try driving as short distance with it disconnected. The reason for excess smoke is too much fuel (worn injectors not atomizing correctly and dodgy fuel* ) and too little air (blocked air filter) . Diesels are simple to diagnose in general but you should get it done soon or you will ruin the bores from excess fueling .
The reason bosch use leather for the pump diaphragm is that they haven't found anything better.


i have filled with diesel in places where the fuel was the cause of the engine smoking and in fact one place has been prosecuted for "watering down the fuel" with waste turpentine!! .The toyota i was driving at the time suddenly started belching clouds of smoke and it didn't clear until I had used all the fuel and was running stuff from another place.

Your use of synthetic oils also explains the oil leaks. These engines were designed to use Mineral oils and the chemical make up of synthetics doesn't work with the type of seal design used in most early mercedes. Besides the manufacture of synthetics is bad for the environment.