Add all the files to the master session, and then render in source mode to DPX. You can choose to render to another resolution if you like. (Just change the Timeline resolution on the config page)
Copying of the “data” directory is generally not a recommended way to moving over postgres databases. The only recommended way is to dump, and restore the database. Or alternatively, if you export individual projects, you can import them into a new database.
Of course in your case, since the older installation of postgres is no longer running, it is not possible to dump out the database, or export individual projects.
I suspect you are running into file permission issues, or something like that, but I can’t be sure.
The database backup is definitely scriptable. You can look for postgres documentation for the pg_dump command.
Also – it’s always a good idea to use multiple databases. You don’t have to store all the projects in one single database. You can choose to divide it by project/month, etc.