Hi! I manage to solve the interpolation problem in the texture.. now it should look ok when pixelated is checked.
The problem with the preview is not due to interpolation. In the image, each colour square we see as a pixel is actually made of 9 pixels. Laigter just use the real pixels, so the light will affect 9 pixels for each "pixel" you see in your image.. i'm not sure if i'm making myself clear here!
I've tried to make a pixelated preview with a shader, but no luck till now.. if i manage to do so, i'll let you know!
The texture interpolation fix will be available in next release! so stay tuned.