I figured out what the problem was. The Blog page SQL query was modified to only include posts of type "Blog post" but the COUNTER query (to determine how many exist) hadn’t been modified to include only "Blog posts". Will try edge cases again to test but I think I’ve got this one.
EDIT: Totally fixed the problem. Not sure whether to "bump" blog posts in the forum if I just edit the post. I’m going to not do it for now.
EDIT: Testing editing items and new redirect.