AFAIK the answer to both is No.
As far as I know, the frame number padding can only be configured from the command line:
From the wiki:
-o or --render-output <path> Set the render path and file name. Use // at the start of the path to render relative to the blend file. The # characters are replaced by the frame number, and used to define zero padding. ani_##_test.png becomes ani_01_test.png test-######.png becomes test-000001.png When the filename does not contain #, The suffix #### is added to the filename The frame number will be added at the end of the filename. eg: blender -b foobar.blend -o //render_ -F PNG -x 1 -a //render_ becomes //render_####, writing frames as //render_0001.png//