Please explain or point me to documentation about how Graphics3D and Directive work with plotting software like VectorPlot3D. For example, I want smaller arrowheads in the attached notebook so I can see what's happening. I'm still looking and experimenting but haven't found documentation that helps, and experimentation has been unsuccessful.

Is there graphic that creates a 3D vector field with a single arow vector that can be moved around either by entering coordinates or with a manipulator or both?

I suspect there are more elegant ways to define the attached notebook. Suggestions would be appreciated.