How to add font awesome down arrow to dropdown menu / folder ?

Site URL: https://shaferrealestate.squarespace.com/

How to add font awesome down arrow to dropdown menu / folder ? 

I was using CSS with a down carrot but suddenly yesterday it stopped working (yesterday, Squarespace did some sort of update that conflicted with my parallax code inject AND the down arrow)

Here's the CSS I was using
// Style Arrow Dropdown Menu
.header-nav-item.header-nav-item--folder a.header-nav-folder-title:after {
  font-family: FontAwesome;
  content: "\f0ab";
  padding-left: 4px;
}

Also I had this in the header 
<link href="//maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome.min.css" rel="stylesheet">
<style>
 

I would like to use the circle down arrow
<i class="fa-solid fa-circle-arrow-down"></i>

Site I'm currently building out 

https://shaferrealestate.squarespace.com/
PW: Shafer

 tuanphan!!!!! You solved yet another issue.  Seriously, I cant thank you enough!

now if you just had a solution for parallax 😜