Your capture has the same luminance, since, as Mike explained, capture is just a transfer of data, nothing is done with the image. If it looks different on your monitor, adjust your monitor and/or the display on your camera.
As Jon said the scaling is murderous on rendering speed as is the noise reduction. If you leave both out, keeping the scale to 100% and no noise reduction, throttling back on the quality settings to around 4 you will see a marked improvement in rendering times without visibly affecting quality.
Why did you scale to 102%. Is that the whole time line or just a single image? What were your quality settings and encoding choices, CBR or 2-pass VBR, audio settings, etc.
The PC is pretty weak, but 43 hours seems rather long.