Site broken, builder won't load

I tend to have issues with Divi Updates (I've done all the normal getting rid of cookies and local data and all that stuff), but this one really has me.

First, I'd been trying to edit a footer for awhile, just add a page link to it, but it would time out and give an "unknown error." So I decided to update the theme. We're using a child theme, no big deal, worst case, the site is down for an hour like last time (!).

This is worse. Now all the content other than header and footer are gone from the homepage (other pages are fine). Not only that, but when I try to load the Divi Builder, I get the "Divi Builder Timeout" error that tells you to check your plugins.

Here's what I've done.

• Deactivated all third party plugins (and one plugin that's Divi but whose license expired so I'm working through all our pages to remove it since we won't be renewing it).
• Removed all data including cookies and local storage
• Deactivated and reactivated the child theme

I'm honestly not sure what else to do, and until I can fix problem number two, I can't fix problem number one, and therefore our site isn't working for anyone who visits.

Help???