keeping the old one as a reference until I'm sure I don't need anything else from it
Yes, a wise move.
The 0 Kb access database files can not be repaired I am afraid, after all those files are saved as 0Kb files so they're not containing anything that can be repaired. There are utilities, many even, that claim to be able to repair corrupt databases, www.officerecovery.com
is the longest existing provider of such software. There are cheaper ones as well.