On the resolution, 6x4 at 300dpi is scanning at 1800dpi.
I've always had problems getting decent colours fom negs. The colour balancing algorithms rely on a decent white point in the neg to set the balance properly. Epson scan has some options for restoring colours (it's part of the ice package, but has a different name) and I've fond this helpful in slide scanning where the colours have gone. But it does give rather oversaturated results. Better than the faded shifts, though.
My old negs (and some are also 30 years old) scan OK.
One trick you can try on the histogram is to adjust each channel separately. Move the black and white adjusters until they're just outside the range in the film, by the same amount on each channel. Then go through the channels again and adjust finely for highlight/shadow colours, then do the same for the mid tones with the grey sliders. However having said that, I prefer Bez' approach - scan unadjusted and do the editing in the photo editor.
Settigns - look OK, but I'm assuming you have it set to film type transparency/negative (or similar).
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