First no department is going to have somebody review all video and audio. They'd essentially have to double their manpower for somebody to review each and every shift video to, "watch the watchers." Instances of a cop letting somebody go for a ridiculous, zero tolerance law aren't going to become an issue unless somebody makes them an issue. The video segments will get reviewed when there's a question of the cop's discretion (i.e. in your example, he walks away from the 'minor' domestic, and the husband and wife kill each other later that night).
If a good cop gets fired for such things, he's not going to survive in that kind of environment, video or not.
BTW, every single example was a real life incident from the life of a friend or family member, not some hypothetical situation.
We have already removed far much discretionary and freedom to act latitude from street cops.
I have friends who are now prominent lawyers, business people, politicians and even a Judge who had youthful discretions that were given a pass by street cops and who took the cops advice to go forward and sin no more and cleaned up their acts.
All of them would have had their career paths blocked and careers killed before they even started but for the generosity and good faith of cops who had their futures in the palm of their hands and choose to give them a second chance.
I would prefer that the next generation of young screw ups are afforded the same opportunity