Jinny Beyer does a lot of inset seams and stars. You might find somethig on her web site.
My first attempt at stars turned out wonky, too. The problem started in the points of each star. To fix, do not sew to the end of the fabric. Instead, mark where the two seam lines intersect and only sew dot-to-dot. If you do this for both the stars and the insets, the wonk might be greatly improved.