I have an early April trip where my connection time in ATL was changed from 1:45 to 0:39. When I called DL to try and change it, I was told that's a legal connection in ATL (they are selling it that way on the website but I certainly wouldn't willingly book it!) and if I wanted to change I'd have to pay change fees and a significant fare increase. I hung up, called back a couple of days later and got the same answer. I presume that being that far out, it'll change again, and by the time it does I'll at least be FO and might be able to get something more favorable.
39 mins is legal but pushing it. You just got a bad set of agents. A schedule change is a reason to be able to shift flights as needed. Being a FO or not doesn't matter. Given that it is April, wait for another sched change, which there will undoubtedly be and shift it to your preferred flight then.
FO doesn't exempt you from SDC and doesn't qualify you for same day standby either. You need Gold for either of those.