The CSS Menu action has a setting under the toggle “Size and Shape” for the menu content width… yours is set to the default of 7 ems. Check the box marked “Use Content Width” instead.
Thanks my brain was fried from staying up too late!
I had “Use Content Width” checked but had more success today when I unchecked it and set each manually in the respective main and sub menu panes. Then just to try it again, I checked the box and was able to make it work that way as well. :-/