This was sort of inspired by the terminator T-1000 from Terminator Judgement Day, and Bumblebees knife hands from Transformers 1.

For print settings:

I would recommend a .08mm layer height (or however fine your printer can handle). 

Yes supports, I prefer tree and using a Top Z Distance of 0.15mm so the supports can come off easier

Printing them thumb-side up as shown in image 7 because the tips of the blades are too thin to print when pointed upright. I have found that this is the easiest way to print for quality, and ease of support removal.