Customization of header area

Hi I’m trying to set-up the Nelo theme.

I have my own custom header graphic that is 960 x 175 that I would like to use. I see that the container for the theme is only 900; can that be enlarged without causing any other issues? If this is a problem, I can adjust the width. The real issue is inserting the full width banner into this theme that has a text title header and small image as header. Please advise what I need to do to make these adjustments.

Also, the intro text is too large and I would like to insert a “read more” halfway through the post and have readers click on it to open up a new page with the full article. Since this is a custom home page that does not use the visual editor, I don’t know how to do this. Please advise.