For running J!5.1 you must https://fabrikar.com/forums/index.php?wiki/update-from-github/ or include the new file manually https://fabrikar.com/forums/index.php?threads/joomla-5-1-and-fabrik-cannot-find-files-error.54473/post-285151 See also Announcements
Please see our announcement here.
Not sure what you are doing. Tables... with JCE? So this is just text, painting, nothing to do with Fabrik/data/database, CSS coming from JCE? Then it's not Fabrik doing the CSS. Use your browser console for checking CSS.The tables that I build in the form