If you give the longest word in your navigation 5 spans instead of 4, and reduce the font size a bit at the last breakpoint, you can move right down to 230px wide before those text links start bouncing into each other. Or, if you change Reservations to Bookings, to have a shorter word, you can stay with the 4 spans.
I see that you have used a subgrid and subcolumns to position the menu. It is kind of complex. Check out what I did. I used a container, but I popped the text links directly into that container, and the positioning was done with the 'push' feature that you find in the layout tab.