IANAL, but I did take an IP law course. If I recall correctly, you have copyright from the moment that you create the work. You can have it officially registered at a later date, however, you might be limited in collecting damages to infractions after the registration date.

I'm not sure what happens if they registered the copyright. Presumably you could sue them if you can demonstrate that you were the true creator.

I don't understand the part about sending a passport.

I do think that filing a DMCA notice is certainly the easiest way. Google has to listen to that.

I don't understand what you mean. If the document was written only 8 years ago then its still got decades of copyright protection. You don't need to do anything besides write the document to have those rights.

Then call the police if they are committing identity fraud.