I know where you’re coming from, as being relatively new to WordPress myself (last 2 years or so) I’ve had a lot to learn with both the positive and the pitfalls. It’s always worth remembering that while WordPress is an amazing platform with a huge array of community driven plugins and themes that’s also where the bulk of the problems come in with badly written content that doesn’t conform to the WP API. When you have something that doesn’t do things by the book you may not notice a problem at first, it’s when you run something complex like SP along side something badly written that you will notice issues. And what’s really unfortunate / infuriating is these issues nearly always stomp all over all other plugins, taking precedence over something that does fully play by WP rules such as SP.
It’s always worth checking out the rating, support questions and developer response on any plugin you’re thinking of adding from the WP repository, some haven’t been updated in a long time, some are riddled with problems with no feedback from the developer and some just plain don’t work. It’s a real shame but just adding plugins that you think will work out great and don’t is really the fault of the plugin / theme developers, not you, not us and not WordPress. I guess what I’m saying is research is important, and you can’t expect every free plugin from the WP site to simply work and not cause problems elsewhere.
Yes, your site is visually looking great! I also think Barebones theme fits it perfectly which is nice to see. The font issue isn’t over of course, it just might take a little more investigating to figure out.
Are you getting icons against every forum menu item in the admin panel / WP dashboard? These are also fonts / glyphs.