Order of Stylesheets links in index.html file

[RQ16]

Your stylesheet on line 6 will be overridden by the external font awesome stylesheets on lines 8 and 9 which makes it difficult to override the default icons font size. Move your stylesheet link below the font awesome one (remove the duplicate fa link), then you can more easily override the defaults (without having to use !important or inline CSS).
You have tried to set the font size in your CSS (line 361) but it did not work because of this.