What do you mean Is there a better way to achieve that? that is actually a perfect unique menu.
Sorry for the confusion, I think Basanta is using the latest beta version that is why he got all the font-weight of Montserrat, you'll get that in the next release too.
But if you need an immediate solution for adding Montserrat font-weight 100, please add this to your child theme's style.css file.
Hope that helps,