If you made an 8x10 print from your 4x5 negative it would have twice the fuzz of a contact print. So if you started with an 8x10 negative to make an 8x10 print then the fuzz doesn't get magnified.
Try a 65mm or so focal length.
To prevent vignetting the pinhole must be very thin. The real reason for the dimple and sand technique is to produce a pinhole with a razor edge to it. Don't use a needle of the size of the pinhole - use one that is considerably larger. You don't make the hole by pushing the needle through but by using the tip of a much larger needle to make a nice dimple.
You can examine and measure the pinhole by putting it in the enlarger's negative stage and looking at a 10x blow-up.
After the hole is almost, but not quite, big enough with sanding use just the tip of a smaller needle (one still larger than the hole) to burnish the hole to the right size.