I have disabled the Get App button in the Header section of the theme options panel. It does fit now but you still have to figure out how to manage this in the lower resolutions (iPad) since the theme is responsive. Let me know if you need any more help.
Regarding the second query, the theme operates on the assumption that a one page template is composed of several page sections and you can choose these page sections in page edit window (overrides the theme options) or the Single Page tab in the theme options. I just had to uncheck the “Showcase” section in the page edit window (see below screenshot) since its contents are already part of another section chosen by you named Features. Pls go through the first section titled Installation in the documentation for a better explanation with screenshots of the page sections and related page templates which utilize them. Thanks.
Hey – sorry for the delay. Yes, you can center any content in a full width page like the FAQ by just wrapping the content inside [segment] shortcode. I just did that on your site and it looks centered now. You can read more about this shortcode, its purpose and the many options it provides for setting various backgrounds including parallax one etc. in the documentation (just search for segment since the documentation has so many pages).