Hi there!
Sorry for your experience.
Unfortunately, the Restora template and SP Page Builder 3 are not compatible with Joomla 5.
The SP Page Builder version 5 is compatible with Joomla 5 though. May I know why you didn't update your SP Page Builder, please? Was there any issue with SPPB 5 for you?
It would be so kind of you if you restore your last working backup with Joomla 4 version, until the Restora template gets Joomla 5 compatibility update.
However, for your console errors the following troubleshooting points would be helpfull too:
https://www.joomshaper.com/documentation/sp-page-builder/troubleshooting#i-cant-save-page-blocked-by-cors-policy
Best Regards