My theory is that the DCEU and DCU are two different universes, and Peacemaker S2 is an entirely different universe to The Suicide Squad and Peacemaker S1, with them essentially just being a springboard for new stories without creating a new backstory.
Well... I don't know about that. It's a theory though. I just think in the DCEU, the Quantum Unfolding Storage Area has an unexplained backstory. I mean, the way I see it, Rick Flag Sr. might not even exist.
I've got some thoughts on the short films.
All years are technically speculation, but:
1975 - The Confession
1978 - What's Wrong With Mom?
2017 - The Nurse
2017 - Blund's Lullaby
2017 - Innocent Souls
That depends on if new universes are being created as composite realities or it's a timeline replacement. We can never truly know right now because The Flash didn't explain it to us.
Could be an old poster. That kind of thing is seen in the Arkham games and they're set many years later... but it could also be before too, so helpful information.