What you have to do first, in order to play with your shadow on an element, is separate it from the item. Click and hold the right mouse button on an item's style (fx) settings, then choose "Create Layer". Then select that shadow layer and choose "Transform--Warp"; this allows you to stretch the shadow in certain parts to make it look as though this part of the item is farther away from the paper background. After finishing the distortion of the shadow, you can use a very faint and soft eraser (about 4-7% flow) to go over the areas that you stretched out, as shadows get fainter when they fall farther away from the item.
As for your first request on changing how the shadow looks relative to the crumple of the paper, you will have to be creative in replicating the look of the paper on its shadow with the warp tool (as above). Since the shadow doesn't show that much around the edge of the item, I think it might not be worth the extra work to replicate the crumple exactly.
Here's an example: