When aligning my header by having the Flex layout row, horizontal end, and margin sides 35px it lines up perfectly and behaves exactly as I want in both Safari and Chrome.
In Firefox it wraps the words of each menu item and looks bad. In IE it doesn’t word-wrap but the breakpoints seem to have broken as the menu will extend outside of the browser window.
If I reduce the font size significantly it will stop occurring but unfortunately the reduction required is too much and ruins the design as well as makes it difficult to read.