From what I see you have started with a rather challenging system for learning SGP and astrophotography. SCTs are long focus and are subject to mirror flop. Can I suggest starting with a simpler system Something like a small refractor - one of the many 80mm F/6.3 ones for example. Even a ST80. The shorter focal length makes all the set up easier and the focus system will tend to be more direct and not subject to backlash. This assumes that you have a small refractor, I wouldn't suggest going out and buying one, however they do make a nice complement to a longer focus SCT.
Well, it shows that the focuser is working and that you appear to be one side of the best focus position. What I'd do is increase the focus step size, instead of 20 more like 40 or 60. Also reduce the star size, 6 seems a bit big and you may be missing small, in focus stars.