I think you did a great job. And remember, it always looks worse on practice fabric than on a quilt top. On a top, you have patterns and fabrics, and if you use a thinner, blendable thread, you will get texture and not see so much of the backtracking misses. (Even pro's aren't perfect!) Also, I just took an online class and got a great hint on backtracking....slow way down. It's easier to hit, and by using the thinner thread, if you're off just a tad you really can't see it. It sorta just disappears.
One thing that was also suggested in the class is to keep these for a few weeks. Once a month or every couple of weeks, compare the old with the new practice so you can actually see your progress. Amazing how little we realize our improvements! And feel free to mark any lines necessary. Even pro's quilting for years still do this!
Great job! I think you're doing wonderfully. It really does look like you're well on your way :)