First - nice, lengthy post breaking down the film...it's been awhile since I've seen the first four movies, so you helped fill in some blanks in memory. So thank you for that.
Second, regarding the O'Conner prison scenes - I actually agree with those who say it was a pretty worthless sequence of events.
Really, I believe it was just a portion of the film that the writers and producers threw in to give Paul Walker something to do for 10 minutes of screen time, and to make it seem like his character had an actual contribution to make in this film.
Let's be honest: since they rebooted this franchise with Fast & Furious 5, these films are now more about The Rock and Vin Diesel than Vin Diesel and Paul Walker. And I'm sure that adding Jason Statham to the mix will only further bump Paul Walker's role down the list in importance.
So rather than make O'Conner seem entirely useless to this entire film's plot, they gave him a segment that shows that he still has some police ties in the US (as his contribution to the team's varying set of "skills"), and he got a nice little action scene on top of it.