I read your linked post, and it seems having a footer widget brings back the next page option?
a) If it was so we would have told you so from the start. At first WP would hide the option "Scroll infinitely" if you didn't have any footer widgets, so adding a footer widget was necessary to make this option show up (so you could uncheck it). This is no longer the case.
b) I linked to my post to convince you that, despite what you thought, turning the blog back to normal is a CSS editing matter. Notice my first reply above:
"Most themes used to have older/newer navigation links on dynamic pages, but WP removed them in favor of infinite scrolling."
WP didn't change the php of the themes, WP only removed the links. The function is still there, and the links are still there (as you can easily see if you check the bottom of your March archive page). It's just that the links are hidden on the main page, so you can use CSS editing to disable the I.S. and make the links show up again (as section D of my post shows). Check my post again: I added the CSS required for Piano Black. Copypaste it into Appearance > Custom Design > CSS and click Preview to see for yourself.