1. Some sidebar locations are wrapped in a fixed-width container, as explained in this tutorial. The location “Secondary Content” you have selected falls in this category. To get the sidebar expand the full width of the viewport you need to select one of these locations: Header Sidebar, Header Secondary Sidebar, Main Sidebar, Footer Sidebar, Footer Secondary Sidebar.
2. You won’t be able to get a 750×132 logo to fit inside the navbar without significantly altering the entire logic behind how the navbar functions. For example, I don’t see a logo of that size fixed to the top while scrolling or having a navigation menu next to it, which is how it looks right now on your website. if you could better explain how you would like the logo to fit in that space and how the navbar should behave I might be able to help you further.