OK So my developer went into the CSS and fixed the problem and a few of the other problems caused by the various updates. The lightboxes was my bad, apparently there were two widgets running at once somehow? Anyway.
To get the galleries back I had to conform to the new approach so what I did was insert a gallery from the ‘add media’ tab… and transferred over the image numbers to my custom gallery so they showed up as they were posted before, in the right order. Otherwise I would have had to build all of the galleries again from scratch, which was sort of annoying since I’d had them all uploaded to the posts specifically. If there is, in fact, a way to capture the images from the post itself like before, I would be glad to find out what that is… but I couldn’t figure it out.
Anyway… It doesn’t seem I can delete this forum thread so I figured I’d post to say I resolved the issue and how I did it. It wasn’t a big deal, thankfully.