For menu font size, there is “Main Menu Font” option which is for “Main Menu” not “Top Bar Menu” as I mentioned above. Actually, the “Top Bar Menu” is not designed to be in the Middle or Bottom Bar, but in the Top Bar. So, I suggest you use the Main Menu instead, which has more styling options. See screenshot below:
The ellipses should automatically appear when the category is listed exceeds the content width, it is a toggle button to show a drop-down menu. The CSS code you use is to hide all including the category list, not only the ellipses. We may need to see the error for further investigation.
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