Social icons: What font is used? Can I use more icons from that?

Hi everyone

I am working on a Twentysixteen theme, it is fun, it progresses and I get closer and closer to what I plan to have as the result …

I use the Event plug-in, which is very powerful, and I would like to include two icons per entry: One for a external website link, on for a link to the Facebook Event.

I found a nice icon through Google icons. But maybe there is a different way?

(1) I ask because the theme as it is offers icons for the social menu already. Where do those icons come from, what is the theme’s source? Because, maybe that source offers further useful icons, and I could just choose from that font?

(2) And since I am asking anyhow: Would someone know how to use the Facebook icon as used by the theme in the footer somewhere else in my content? How would I do that? I do fail …

And (3): My social menu icons have a circled border around them. I fail to delete that border. Any ideas of how to get rid of it?

Thanks!

Best,

Stefan