Just watched it Leo, it was fun to see travelling with plank. Crazy question if I may, To get rid of fuzziness couldn’t you try to mount one of those abrasive brushes on the CNC? Not always but those sea horses do not have delicate details to worry about or so I think.
Obviously you would need to create a specific path for that or use one of the used for milling them but changing the bit by one of those vertical (or should I say axial?) brushes. They come in different grits and diameters, have you ever tried that on the cnc?
I wonder if you can remove those raised grain fuzzies with a Sand-o-Flex which is a flap sander with 8 flaps with each flap having 8 fingers. I used to use them to help sand odd shapes with raised grain. You can buy models that mount to a motor shaft or be used in a portable drill.. I have had one of mine for close to 50 years.
Since the flaps can be extended as long as you like and the sander can use sandpaper up to 600 grit it can be as gentle as you would like. I do understand what you are saying about burning the grain to achieve the distressed look you are looking for. Interesting project.