Alberto,
this all can easily be done without using the skeleton tracker at all. Just use the multi-touch panel and you are all set.
If you want to use the tracker, you have to define for yourself when and how you want to interact with the layers. Shall they always react to your hand or only in a specific depth!?
Rotation and scaling can be addressed by using the distance between two points and its rotation angle. Use the "Angle Distance" node for that or one of the vector nodes.
Markus