I think a great way to improve the usability in the website is by using areas for the page’s image. Allowing the user to go to the next page and the previous, without much effort on small viewports.
Pretty much what happens on a kindle for example. You have a left area of the image where you can click to go to the previous page, and a wider right area of the image so you can go to the next page.
Try clicking the image in the example in fiddle. The only thing that would go different is that in the site structure there is no need for the onclick in the hyperlinks. Use normal href tag instead.