Cool shots (I especially like the frog) and neat shooting technique.
For shooting the frog, I would have been tempted to use my 70-300mm VR stopped down to f/8ish and a maybe a 36mm extension tube. Not sure how I would have done the valve spring...
Shallow DOF is something I think everyone that shoots macro fights. I find, a lot of macro subjects are small enough to effectively be 2D so a shallow DOF can work. Your picture of the frog and mine of the butterflies are examples of situations that are definitively not 2D, though.