Hello Jim,
Welcome to Microsoft Community.
I understand the inconvenience this issue has caused you.
Your core problem now is that you are stuck in a preview/beta channel, which is why simply reinstalling Office gives you the same broken version back. The standard rollback failing with error 30183-27 (400) also points to a channel or permission issue.
Your machine is enrolled in the Office Insider Program (either the Beta or Current Channel Preview). This is why uninstalling and reinstalling just pulls the latest preview build. The solution is to first change your update channel and then force an installation of a stable version.
You can manually Revert Using the Office Deployment Tool (ODT):
Step 1: Download the ODT from Microsoft: Download Office Deployment Tool from Official Microsoft Download Center
Step 2: Run the downloaded .exe file. It will ask you to extract files to a folder. Create a simple folder for this, for example C:\ODT:
>> In the same folder (C:\ODT), create a new text file and name it configuration.xml.
>>> Open the file in Notepad and paste the following text into it. This configuration tells Office to install the latest version from the Current Channel, which is the standard stable release.
Note: If you use a 32-bit version of Office, change OfficeClientEdition="64" to OfficeClientEdition="32")
Step 3: Open the Command Prompt as an Administrator.
>> Navigate to your ODT folder by typing: cd C:\ODT
>>> Run the following command to download the stable Office files based on your configuration:
setup.exe /download configuration.xml
Step 4: Once that is complete, run this final command to install the stable version over your broken preview build: setup.exe /configure configuration.xml
Please let me know if it helps.
Best regards,
Alex | Microsoft Community Support Specialist