1) Yep, your thinking is right on. Try to seal just the faces of the tile.
2) Yes, seal the mosaic. It will help. Especially on the crackle glass that may otherwise take in some grout and permanently stain it. The mosaic tiles with the deep embossing are going to be time consuming to clean the grout from. Use a toothbrush to help clean them (experiment with bristle stiffness to see what works best). Taping the tile isn't exactly practical. But some folks find taping to help somewhat.
3) Ok.
4) A bucket of patience and a dowel sharpened with a pencil sharpener. And did i mention patience?
