Reduce the width of the mega menu in dawn theme to max content

[ojoroh]

I'm using the dawn theme and I can't figure out how to reduce the width of the mega menu in my main header to be just the size of the content (like the dropdown option).  I also need it to be centered under the dropdown option.  Right now, the mega menu takes up the full width of the viewport, and my second mega menu (more) is left-aligned for some reason. I've tried the fixes I've seen on other posts like adding width: max-content !important under various functions, but none of it has worked.  All it does it reduce the width so much that only one or two characters fit on each line and the mega menu becomes extremely long and illegible.

[ojoroh]

Dawn