Did you switch integrations? The bigimage userid prefix is not a big deal if later you switched integrations. The userid being prefixed on the image just means you already ran 485 upgrade. So you where on a 5.0 version.
Just make sure you have all 5.3 files uploaded and run 5.0 thru 5.3
Duplicate mysql errors are not a problem
If your site runs fine your good to go dont worry about anything. The news thing is always going to report 5.3 is available and your current version is also shown on that stats screen in admin