? 1 - the flooring is tongue & groove how deep should I route the actual ? cavity (for lack of a better word) for where symbol will sit? Should it go ? all the way thru? Is there a good rule of thumb?
No need to go deeper than the top of the tongue & groove- that's the limit to the life of the floor.
If I were to do this, I would use Ebony and Bloodwood or Rosewood.
I wouldn't stain it. Chosen carefully, those woods will be pretty close to the colors you want.
Best of luck, and let us know how it comes out!