Nice, I'm a huge fan of the design. Really nice. Don't worry about scale, we can deal with that at the end. It will need to fit into a 2x2 tile for the game.
One question: is this intended to be a hi-poly model that you use to bake a normalmap? Or is this the final model? If it's the final model, I might suggest not modelling the cracks on the top and instead creating them through the skin/normalmap. In-game, the difference will be minimal and I imagine it will save quite a few polys. Not a requirement, just a suggestion.
What's the triangle count now?