Thank you but it appears you didn't read my question. Doing what you suggest would create even more problems for me: If I unlink the PC, then the Onedrive folder will no longer appear in File Explorer, which means I can't do #3 and #4 in my question. Also, I don't know what this unlinking would do to those files that Onedrive automatically synced (again, an unwanted behavior) to the cloud; but, I need to make sure those files are local on my PC and no longer in Onedrive - there are thousands of files in dozens of folders which I did not and do not want on Onedrive but do want locally on my computer. As stated in #2 in my question.
If you are able to respond comprehensively to all of these issues, that would be great. I would be happy to explain further if something is unclear.
Also, as mentioned, I want to prevent Onedrive from ever reenabling its automatic syncing/backing up by itself.
Thanks.