I’m sorry Neo, but we’re really moving past customer support now. I was under the impression you were updating and the entire theme was breaking with PHP errors, which isn’t the case at all. For these kinds of minor stylistic customizations you’re really going to need to contact your developer and I’m sure they can get you squared away with a couple of billable hours, for any slight tweaks that might need to be made with their CSS changes.
As far as the template part files, it is important to note that “content-single.php” of the previous version is now “content.php” and “content-single.php” no longer exists in the theme. So,
content.php is what’s responsible for displaying single posts. — But this is the only change in this regard. However, in your case you have many files that your developer has added in there.
What your developer has done with a
themeblvd_posts function is a little cumbersome and there are probably better ways that could have been accomplished that without copying that entire function over, but that’s how he/she substituted a lot of your template parts in, in opposed to filtering.
This is all outlined here: http://dev.themeblvd.com/tutorial/editable-content-files/