It is a difficult pose, but I don't know if I could do any better. It would probably be hard to find a good photo reference. It's making me want to try though.
(I'm always stealing other people's ideas!)
As for clothes shading, I usually think of it like shading a cylinder or some other such object, except trying my best to follow the contours where things stick out (like bosoms or elbows or whatever). I really struggle with it too.
But I just gave you credit for #34!