Many good articles on making a Foucault tester. See Richard Berry's book "Build Your Own Telescope" (which is probably the easiest to understand) or Texereau. Richard uses a slitless tester whereas Texereau uses a slit. With Berry the formula changes as you are measuring the radius of curvature not the movement of the knife edge. Because the knife and slit move as one you a measuring delta R. Tex measures the movement of the slit to the light source so the measurement becomes 2 X delta R. I have been using a slitless tester for the last twenty odd years and so far so good.
The Ronchi for windows is a procedure that Ted Lumley used, but we used to use wire to take the form. See Laurie Halls webpage:
http://www.turbofast.com.au/astrotel/ronchi1.html
Ronchi tests are usually qualitative, the Foucault will give you a quantitative result.
The resin lap may be the cause of your micro-ripple (dogbiscuit) a true pitch lap minimises it. A good quality burgundy pitch (Gugolz) makes a difference, it's just hard to come by.
As Cristian said, you could mask the TE, but you will reduce your effective aperture. One 14" that I worked on had an edge that was soft annealed, I have the option of either trepanning another 15mm off the diameter or masking the edge. It's simpler to do the latter!