From the screenie and the log entries you posted, the error is happening when the upgrade software is attempting to update the database schema, and encountering an issue whereby it is trying to add a primary key to a table that already has one.
This means, either there's a problem with the schema update scripts, or the upgrade process is unable do what it needs to do to the database/table.
It's unlikely to be an issue with the schema update scripts, as the upgrade process just calls known working scripts in turn (i.e. the scripts are tried and tested from the previous version upgrades). So this leaves the DB access thing.
At this point, I think your options are:
- Call Symantec Support
- Backup/Copy/Restore the DB to a test machine or VM and try the upgrade again in an isolated environment where you can confirm there is only one Management Server connecting to the DB.
- Try upgrading via v8.0.1 (I know this works), then up to v8.2.0 (I know this works too)
To be fair, it would be best practice to do option 2 anyway considering the problems you've had so far, and run any other upgrade tests on the that environment.