Hey Jeff,
Thanks for reaching out and sorry to hear about the issues updating! The fatal errors were added to the QA checklists as Brian stated in the thread you shared, so hopefully we won’t fall into that issue again. Regarding the safest method to update your site plugins and theme, is to do it in a staging site and test before going live with the changes. I know you mention you develop on the live site, but this is not a recommended practice! You can have a copy of the site running in a local server like XAMPP, or also ask your hosting provider if they have any specific tools for this (1-click WordPress Installs, etc).
Please let me know your thoughts about this,
Best,
Nico