I know you think he stood by but i disagree. He called out her abuse when he saw it. He mitigated the damage for the girls as best as he could and keep them safe while under her roof.

I know he took action and tried to confront her (useless as confrontation may be), and I do think that's great. However, it's better to prevent damage than attempt to repair it. The longer he waited to report it, the longer they suffered. And no matter how hard he tried to fix it, they will always have that trauma because they experienced it. His actions may help them a little bit, but in the long run they will still have trauma and his actions are like a bandaid on a bullet wound: it won't do much.

I am saying this as a victim of abuse. My parent tried to protect me from such abuse (for the most part) but they still enabled the abuser and it didn't help near as much as preventing the abuse altogether. It's just not how it works.

As for him finally reporting it to the father, I do think he did the right thing by doing that. I also think there were other earlier opportunities to do so, but I digress. I agree that he did the right thing by telling the father, and maybe he could've approached it better, but he still did it. He should definitely testify against his girlfriend, and I actually think that will be the determining factor of whether or not he's TA. He's witnessed so much, he can help save these children, and that's the perfect opportunity to do so.