1. yeh but a over 130cm long blade with out anythign special looks boring to me ;) The sawtooth are only for optical reasons ;P
But actualy only the top 1/3 of the blade is the effective area (at least that coutns for straight medival swords, no clue abbout katanas). So if you attack with that long blade the sawtooth should not be touching the enemy anyway.
2. Same as 1. Only optical reasons.
3. Noep, I thought abbout it, but then it wouldn't have been even close to a katana anymore. Seems the shadow on the groudn causes that illusion :P
4. I tried to simulate that without the need of creating textures first but were not able to :/
And on your pic i see that over 70% of the baldes width are sharpened.
I should keep that in mind for the next time ;P