Obviously, you won't get professional perfection from a budget priced scanner (by professional standards this is budget equipment). I wonder if 48 bit depth is tending to pick up every bit of imperfection. Have you tried reducing to 24 bit to see what happens?
As for your examples. I have had a look at what appears to be the more difficult image and I think your sharpening technique may be accentuating the background noise. This is really a case for one of the more expensive sharpening programmes.
However, I have had a go with my suggestion for selecting and feathering (5 pixels) the main subject and just sharpening this part of the photo using standard Unsharp Mask. Radius 50; 3 pixels; 1 Threshold. This is the maximum I would use. I haven't done any other processing. A slight tweak with Curves etc might also help to enhance contrast.
See what you think. I reckon this is about as good as you are going to get. But, as I said previously, it may be worth getting some done professionally and comparing the results. Remember though; film, negs or slides, is still one of the best methods for archival storage of photographs and if kept under good conditions, should outlast CDs.
