Replaced Fira Sans (311 KB) with Route 159 (55 KB). Even if it's not the perfect typeface, I'll keep looking for lightweight replacements.
If care about weight, have you considered font-family:sans-serif? It's even lighter at 0 KB. ;)
Doesn't that cause concrete pixel width to fluctuate based on the auto-selected font? Could thereby cause hard to spot layout errors.