The piece is printed best standing on the back as positioned in the STL. In general support is not needed, only the hole at the back could use some support if you want it to look super sharp.
I printed with a 0.4mm nozzle, 4 walls, 7mm cubic infill distance. I highly recommend 3D infills like Curas or Slic3rs "cubic" when you need maximum strength.
You really don't need more infill, the layer adhesion of the average PLA at the right temperature is much better than you might think. And as the layers run at an angle to the centerline the effective surface area for layer adhesion is increased.
You will need at least 150mm print height.
Depending on the thickness of the blade and the dimensional accuracy of you printer you can choose from two files with different slot widths.