I used TheSkyX's @Focus2 to set the focus on a 5th magnitude (or thereabouts) star near Jupiter. I think the focus is ok. I also think the collimation is reasonably ok.
You really need to get experience focusing on planets to advance your imaging outcomes I have to say!
After initially getting a sharp edge to the planet & adjusting the gain such that any detail is apparent an "increase" in the gamma value creates greater contrast to allow finer judgement of the clarity/sharpness of any visible features on the disk...for the actual capture this should be returned to the default vale btw.
Jupiter has numerous "indicators" to gauge optimum focus: the festoons or thread-like filaments that project into the EZ, getting these gossamer-like features as sharp & well-defined as possible is a good approach & at the same time in the EZ there might appear small "splotches" of dark matter (often associated with the festoons) as additional guides.
Another indicator are the small, circular-like white storm spots, these become more apparent as you get closer to optimum focus, especially concentrating upon the smaller ones if they are visible further N or S of the Eq.
The darker NEB & SEB, definition alters from a bland darker colouration out of focus to a much clearer set of features with clear definition in the edges of these features where the borders are curled, curved or fluted - & lighter & darker details reveal themselves within these dark bands...
Saturn is relatively easy in comparison: the grayscale used for basic computer screen calibration displays 256 (8-bit) tonal images from black through to white where it should be quite easy to detect the differences between the blackest & all the other shades; all that is really needed is to adjust the focus on Saturn until the Cassini Division appears "blackest."
In average seeing or above, this is quite self-evident: once you have achieved this you will also notice (if the seeing is good enough) that you are able to define numerous bands on the disk of Saturn in larger apertures...
I'll leave Uranus & Neptune for now but there is other information that you might find useful on our website also: accurate collimation is also an essential for good image outcomes btw. (see link in signature)