1) Mikro amp is a plugin that is a small sqaure that controls Winamp. It also lets you turn off Winamp's windows which Winamp not take up very much space on the desktop. The point of skinning it is so your Mikro amp matches your Winamp
2)I'm not sure if this is what you're pointing to, but I think it's the last few pixels on the right side. This is because each block in the grid in the background is 10x10 px. and each window is 116 px. Therefore, the grid doesn't fit evenly and there's a few pixels left over.
3)I don't know
4)I don't know where the link is, but I bet Jones will be here with it soon