With shadow stitching when you quilt this, you've just created a new "mock trapunto" method! I think your piecing is wonderful. Your points are really points (my weak area!) and your colors look awesome. As for twisting in the pressing, if it's just that one long seam, you could try clipping (carefully!) the spot where it joins the other seam, or pick out that one small section and "flip" the wayward seam the right way! I'm not sure that anyone else would ever notice, if you left it just the way it is! Remember, WE are our own hardest quilting judges! Everyone else if likely to ooh and aahhh over the whole thing.