The letters quite small. (.17") If you want to carve them deeper, use a 45 or 30 degree bit instead of the 60 degree bit. However, they will still not be very easy to see. When I cut letters this small, I seal the wood after carving with a coat or two of sealer or clear finish. Then I fill the letters with contrasting acrylic paint. After it dries I sand off the fill paint that has gotten on the flat surface. However, this will be difficult to do with your design because of the raised grid.
What I would do: Use the pocket toolpath, and cut the grid pattern, cutting the pockets with letters 1/8" or so deeper. I would then carve squares with lettering on them to fit the pockets. Paint the letters, and glue the squares into their corresponding pockets.
On further thought, you can get the letters to stand out more if you use a light wood such as maple and apply a dark stain. Wipe off as much as you can so most of the stain that remains is in the letters.
Good judgement comes from experience.
Experience comes from bad judgement.