I have a backup from 2 months ago,
Not good. This is cold comfort but you really need nightly backups as a minimum and even more frequent back ups would be a very good idea.
Once you get that dreaded "access privileges are damaged" report, you are often out of luck when it comes to recovering the file. If you had a recent version of FileMaker, 11 or 12, there might be other options, the makers of FM Diff, offer a file recovery option for example, but I don't know if they would touch a file of such an elderly version or not. You can always google them to find their web site and ask...
You might also try recovering the recovered copy of the file to see if you can get any success that way.
Duplicate the file in the OS.
Run the Recover routine under File Menu.
If the recover is successful you will have a file called "myfile recovered.fp5"
Export the data to a file.
Open a Clone of the Backup.
Try to import the data from the recovered file data.
If that fails, import the exported data.
Duplicate the databases as you do this.
Regular Backups are a Good Idea.
Dealing with Damaged FileMaker Files
What to do when your file is corrupt
FileMaker Damaged Files, Corruption, & Recover
Corrupt / Damaged Files: How to Avoid the Need for Recovery
Title: What is the cause of file corruption?What is the cause of file corruption?