1. Yes, I think BB adds Font Awesome to your site by default. However, I think it only adds it to pages you’re using BB on, so if you’re doing this on a non-BB page, you’d need to add it: https://wordpress.org/plugins/font-awesome
Then you could do this:
.wpsp-read-more a:after {
font-family: "Font Awesome 5 Free";
content: "\f105";
padding-left: 10px;
}