Changing themes

Newbie here. Been trying to build a new site for our firm. Our only designer/developer just left, so it’s up to me to get all the new content I wrote right before he left into a site that has the same look as our old one. Except I picked a theme that is not working at all. First question; Is there a shortcut to loading everything I’ve done on 17 pages into pages with a different theme? Or can I do it the other way around, take the current site and apply a new theme to it. Next question; What is a good WP theme to accommodate pages that are entirely white space with only our masthead at the top, which is white with black and green line art and narrow copy blocks running down the middle? The one I’m using has a heavy black bar that breaks up the white space between the copy and the masthead. Lastly, I’ve only been able to use black type on the white background. On our old site and in our printed materials, headlines and subheads were green. I know how to change type colors in word, InDesign and PhotoShop. Can’t find anything in WP. Maybe it’s the theme I picked. For reference, this is our old site. Have a good laugh, especially if you look at the source code… `