I love machine applique. If I were you I would shorten the stitches in both ways and what I was told is that the stitch has to be 20 % on the background and 80% in the applique. I always try to have the outer stitch on top of the edge of the applique piece, it takes some practice but it can be done. The open toe applique does all the difference on your visibility. Also, I sue stabilizer in the back and each applique is fuse to the background. To tell you the truth, I don't find your work bad, I think we sometimes are harder on ourselves than we should be and don't forget other people won't notice the details unless you tell them to look.
good luck, don't get discouraged. Keep going.
andrea