I've quilted queen size on my 300.00 machine. Just stitch in the ditch. I only sew straight lines. I don't try to pivot and turn the quilt it is just too hard on a large quilt. I tried the free motion but my machine didn't have enough muscle to hold the bobbin tension. So hope it helps to know your not alone in your struggle with quilting. Your quilt looks great, by the way.
Marie