Practice practice practice. I love FMQing. And you are a talent. I am looking at your quilting design. So keep going. It will come. I listen to the hum of my machine and that is how I know to speed up and slow down. You don't have to go at top speed. Go at a speed that is comfortable for you. But just keep keeping on.
We, the viewers look at the quilt as a whole. We aren't interested in whether the stitches are long short even or not. Done is best. And you learn with every quilt.
If you can manage it, take classes from different people, they all have some special tip that will help. Learn a little, practice a lot and take another class when you are ready to progress.
My favorite method is fluff and stuff. It makes sure that all the directions I want to go are free to move. I have seen some people try to FMQ using the sleeve arm of the machine. You can only move what you can control. Use a large table around your machine having a large flat surface with your machine surface. I have made my own. The adjusting bottom of the legs are available even at my small local hardware store.
I'm being so long because I am really impressed by your quilt and I want to see you do more.