OK, off hand I would conclude:

1) your car is not overheating assuming the coolant is full. 180 is correct.
2) Autolite 606 I think is a resister plug and shouldn't be used. NGK BP6 or Bosch W7DC are good choices. I am pretty sure you do NOT want resistor spark plugs. If there is an "R" in the number it is a resistor plug.
3) Solex carbs - OK, the right barrels look from the hood towards the car are the barrels closest to the engine. Those are the secondaries. They open after the primaries. Those are never opening with your linkage the way it is and that is why your car is slow.
4) Choke - can you turn off the choke with the car warm and not have the car stall out? If your car stalls with the choke pushed in when hot then you have either idle set wrong or vacuum leaks or most likely both. You can't set/tune the carbs if you have vacuum leaks. People compensate by setting idle too high.
5) White smoke is I think water vapor - someone else confirm. What does it smell like? If you have water vapor then you might have a blown head gasket.
6) open holes on the carbs? Post pictures.
7) cost to adjust linkage? First you need to find someone who knows how to do it OR have the good MB instructions. I would guess it is an hour of labor.
8) you can synchronize the carbs without having the linkage correct. The linkage that keeps the carbs sync'd is one piece of linkage but it isn't the one that controls how far the accelerator pedal pushes on the linkage. It isn't going far enough.
9) oil on bottom of block means oil leaks somewhere, that is the least of your worries. If you want to know how much, wipe it all clean and see how fast it gets wet. Monitor oil and coolant consumption.