I've struggled with these issues before, and have tried then backed away from the same maximum-size solution.
Fortunately, #2 can be resolved easily by setting input,textarea{font-size:16px}. There are problems with 16px for all inputs (especially if using a custom font with different metrics than the default), but it preserves a significant usability feature. A fair trade, even if it means using system default inside of inputs.
Regarding blurry images, I favor suboptimal delivery of content over failure to deliver every time.
Fortunately, #2 can be resolved easily by setting input,textarea{font-size:16px}. There are problems with 16px for all inputs (especially if using a custom font with different metrics than the default), but it preserves a significant usability feature. A fair trade, even if it means using system default inside of inputs.
Regarding blurry images, I favor suboptimal delivery of content over failure to deliver every time.
Great work on the framework, keep it up!