previous_post_link off by 1, will not create link to 1st post ever

I’m using this code to create a single-post-per-page layout. it works, except clicking previous will only eventually take you to the 2nd post – it never reaches post #1, and the previous_post_link disappears on page 2.

home.php:
http://pastebin.com/q0Z1NX8i

single.php:
http://pastebin.com/WGKc1N2w

footer.php:
http://pastebin.com/FBc4wwmJ