I hope this poor quality image helps. This is a frugally rebuild image of the final arm lock (this round made with the left arm, because my silly camera couldn't make the photo better than in that position). If from that situation you step forward and you tenkan, your hand will exert pressure on uke's locked arm and bring him down.
This may work only: right arm traps right arm, or left arm traps left arm.
When you tenkan (right hand to right hand) do you float uke's right side up before dropping to his knees? What you're describing of uke reminds me a version of soto kaiten I've practiced. Does uke end up facing you at the end of the drop or is uke's body rotated away from you similar to shihonage ukemi?