Since you want to keep the old scales, use caution. Apply masking tape around the pin to protect from scratches. DON'T use a Dremel or any other power tool, or the heat build-up may melt or burn the scale material.

Start with a fine flat jeweler's file, and get a nice flat spot on the end of the pin that has a washer. Then, make a tiny dimple in the center of the pin using a sharp point of a #11 Exacto knife and turning. Clamp a SHARP 1/16 drill bit in a small pin vise, and proceed to drill a hole in the center of the pin. When you have drilled enough to get the bit point about a mm or so down, switch to a 5/64 bit. As you drill down, the washer should come off. (Might need to go to a 3/32 bit next, in some cases.) Use a small, sharp pair of dikes to snip the pin flush with the scales. If the pin doesn't fall out, lift the end of the scale a little, slide a flat knife blade between the end of the pin and the inside of the scale, and push down. You may then have to grip the other side of the pin with small pliers and rotate/pull to get it out. It often happens that the pin gets bent inside, so won't fall out easily.

Yes, usually replace both pins. Easier to find 1/16 brass rod and washers rather than German silver ones.

If the blade is already in pretty nice shape, I certainly wouldn't start with 220. Try 1000 first, and go down if needed. You might try the Dremel #512E 320 grit "puff buffs" first, as those are good at leaving no scratches.