Foto-goofup isn't cooperating with my computer, but in general, tiny cracks aren't terrible. Glazing is, a shiny finish that interferes with the clutch disc getting traction on the flywheel. Try getting a machine shop to grind (not cut) the friction surface to remove the glaze. Another common flywheel problem is hard spots that are difficult to machine or grind away, and they tend to be football-shaped. As the surface is machined or ground the hard spot gets bigger. The spot that shows on the surface is like the tip of an iceberg- - - -there's much more below the surface.
Jerry