darning foot- must have a spring on it. that helps a lot. feed dogs down generally but not a rule. depends on the machine,the batting,etc.
move your quilt fairly slowly, but the foot pedal speed fairly fast.
the movement of the quilt makes the stitch. slower is longer, sometimes looks like missed stitches. slower makes the stitches smaller. practice,practice.
your photos almost look like you were doing a zig zag stitch.
make some squares of fabric with batting and doodle. save them and use again.