It seems a little like you have the brightness set way too high. I strongly suggest that you turn it low untill the background turns black, and the letters aren't "blooming" (they should be rather dark green, but still comfortable to read). If you run it too much with the brigthness too high, the risk of burn-in gets higher.
By the way, my 5151 uses just the same borders as yours, so I think it should be like that. It is not a graphics card, and it is only intended for text, so the outermost space is really there to simulate the margin of a typed paper.