I think the default system font should be a more condensed variant; it would make the system look much more refined. There are a number of areas where it's clear you need more horizontal space for characters. Each character should have less width, and there should be as little space between the characters as possible - just a single pixel ought to be enough at the font size and resolution you're using.

I don't know anything about your font system; I'm assuming it's fixed width bitmap fonts? I don't know how hard it would be to make these changes within your codebase so if it's too much work then don't worry about it.

I've been building a web OS site from scratch for a while now (not as technically impressive as what you're doing) and I just got through a total rewrite of the font classes, so it's at the top of my mind.