I think that the shadows of the file teeth add character and show its history so I would'nt worry about completely polishing them out.
The rate of cooling in the quench is effected a lot by the type and temperature of the oil. Heating the oil a little actually speeds up the quench as the oil circulates better. Peanut oil is supposed to be very good although I havn't tried this myself.
Hot brine is another method and is a lot safer than hot oil, although this may cool the blade too fast especially if it's very thin. Abother tip is to leave the blade just a little bit thicker until you've finished the heat treat then grind down to size.

Are you casting some silver fittings for the handle ?

Rab