Hi, Mark. Shellac has good resistance to water vapor exchange but only moderate resistance to wear. You can put just about any other finish over it and I think that oil based poly is best for floors. You might try cutting the 3 pound cut down to a 1-1/2 pound or 1 pound cut and then putting 2 coats of poly over that. the poly will add an amber look over the orange.
Be sure that the shellac that you buy is relatively fresh. Shellac has a limited shelf life.