Hi,
http://prntscr.com/irwpab
1. You can see from link image:
- Header will be divided into 3 parts, each section has a corresponding width in % (41.66667 - 16.66667 - 41.66667). When the screen size change, although the with in % not change but the width in pixels is changed
-> Until the size in pixels < 200 (Logo natural width) -> the logo size will be decreased -> This is normally in Responsive Website.
2. The setting to Full width just help the logo, header left, header right have more space.
3. I'm not sure this problem. You can try to disable the option "Header Float" and check again.
Thanks.