I don't have specific own experience with this particular freewheel, but I found a picture
http://www.velo-pages.com/main.php?g2_itemId=22673 , which confirms your assumption of a second step on the freewheel, which again is locked by a threaded cog.
It has been my experience in general with dismantling freewheels, that you have to use the two chaninwips in a way that they form an X to take full leverage advantage (see picture from Park website)