Really? I must admit I have no clue how strong the effect was, the warhead at least was only 50kg but indeed it was layout it to effect with concussion "Druckwirkung (Gasschlag)" instead of shrapnel or so.
As mentioned the ranges in Stalingrad are said to have been 120 to 300 meters with a maximum range of 600 meters, I guess more wasn't possible when firing them out of the boxes as they couldn't be raised that far.
Question is for what launcher were these ranges, out of the box I doubt they could be fired up to 2km or 2.2km and that they had a minimum range at all except for making sure that the troops who fired them were not harmed.
I assume the ranges give are either for the "schwere Wurfgerät 40" or "schwere Wurfgerät 41" or even for firing them from the so called "Wurfrahmen 40" what used a Sd.Kfz. 251 as firing plattform.
http://de.wikipedia.org/wiki/Wurfrahmen_40
I guess the 32cm with flame oil could have even used shorter ranges as it ignited an area of 200 m² what is a square of about 14x14 meters.