I do not have much experience with driving 230SL, I have an automatic 280SL. Therefore difficult to comment on how heavy or dynamic 230SL is.
But I think that any of your points 1 and 2 that relate to auto transmission performance are not typical. I think the transmission you tested is out of tune. I also think that the engine is out of tune as well - which would result with transmission not working properly.
My experience with my auto transmission is - it works very similar (in feel) to modern transmissions. You select 4, the car starts advancing very slowly, gear shifts are smooth, no clunks on deceleration. Yes, there is slight clunk and slight rev increase when you hold the brake and select P. Yes, it has the tendency to start faster when you select R. But this is all. As long as engine and transmission are in tune. The engine needs to be in tune, particularly idle, t oproduce correct vacuum, then the transmission 3way solenoid needs to engage properly, meaning the throttle switch needs to be set properly. Finally, the transmission pressure needs to be set properly.
As JamesL said, you normally start with 4 selected. Then the car starts from gear 2. If you select 2, the start is from 1 - for sporting occasions, maybe steep hills - I never used it, actually. I can imagine starting with gear 1, when the car is out of tune might have felt like you cannot stop it as if the brake booster was shot. But this is not typical condition.