Regarding the Barbara thing, I might be wrong but is it possible her age was retconned after IC?
I'm guessing you're getting the whole "she's 13 years older than James Jr.'' bit based on the idea that she became Batgirl around Year Four at around the age of 16?
But its possible that it got retconned after IC. As it is, I'm not really sure whether the whole ''Barbara is the niece of Jim Gordon, or possibly his biological daughter from an affair with his sister-in-law'' thing stuck after IC. And with a 20 year timeline, its possible that Barbara was closer in age to James Jr. and made her debut as Batgirl later? (Then again, there's a limit to how much closer in age she can be...I think a little less than a decade makes sense).
I dunno how Year Three makes it clear he can't be older than Tim Drake, or about his appearance at the Gordon-Sarah Essen wedding. But if we assume he's something like maybe 18, I think its believable that its been 8 years since the Gordon-Essen wedding (which was sometime in the early 90's, if I remember correctly)? That would of course make Tim a bit older. Argh!
Details aside though, the important thing is that Black Mirror established that a character who was literally born during Batman's first year in action was now old enough to be a serial-killer.