What are the difficulties in separating cast shadow from reflected Light and shade?
The difficulty in separating cast shadow from reflected light and shade is that there is very little tone difference between them and makes it hard to determine which is which. However the fact that they fall in opposite directions does help to determine which is which.
The reflected shadow and light follows the contours of the objects how have you shown this in your drawing?
To show how how reflected light follows the contours of the objects I used fluid strokes and hatching techniques as well as following the contours with a putty rubber.