Blender Render:

Yes, my textures in that one are only created at 1280x720, so anything rendered higher than that will lose some quality. Also, going larger will show the limits of the displacement map. Micropoly displacement will definitely help once it arrives. You could also mix in an extra very fine detail to add more imperfections at that scale.
Bump node is being driven by the mat texture,... not sure what you are seeing.
Height is used in the bump node because this is a height map, not a normal map, and this node converts it to normals for the Glossy BSDF
Yup, the 2 subdivision modifiers are there to get around the limit of 6. Also this kept the file smaller than using multi-res, which gives the same end result.
And just one more watercolor look to end the evening.