OCI uses native drivers, period. As does the DRS stage when explicitly set to Oracle. Nothing to doubt there. If you have other doubts, you'll need to enumerate them as I'm not about to try and guess what they are.
OK... that answer assumes they are still being stored in the "Universe" repository, which may or may not be the case depending on your exact 8.x version and certain settings.
CLEAR.FILE RT_LOGnnn where 'nnn' is the internal job number of the job in question. You'll then need to re-establish your auto-purge settings as they will be gone as well.
There are environment variables for handling decimal data: APT_DECIMAL_INTERM_ROUND_MODE, descrption is it specifies the default rounding mode for any decimal intermediate variables required in calculations. The default is round_inf. APT_DECIMAL_INTERM_SCALE Specifies the default scale value for an...
As noted, no - you could use those from a routine and call that after job. For a script you need to stick with either dsjob options or things you can query from the repository.
There's no "better". And of course mine are well documented on the canvas with annotations clearing explaining both what it does and the fact that all of the code is on the Job Control tab. Plus I also get full control over when it gets compiled.