1) You can use respond.js[1] if you don't need complicated media queries. It's much smaller than 15k
2) Icon Fonts should make use of the Unicode Private Use Areas[2]. Screen readers should not attempt to make sense of these code points, and you can add title tags to enhance accessibility.
[1] https://github.com/scottjehl/Respond [2] https://en.wikipedia.org/wiki/Private_Use_%28Unicode%29