I agree with the commenter who said this movie gives people false hope. I also believe that it sends the wrong message. Alot of people believe that forgiveness means to take the abuser back and give him another opportunity to abuse you as though it never happened in the first place. In reality it just means that you are able to heal and move on with your life (separately; not together). Once abuse has reached this level both physically and emotionally and trust has been so seriously violated, that is a bell that cannot be un-rung.
The best thing this man could have done if he truly loved her would be to let her go. I think his whole goal throughout therapy was to worm his way back in. Subjecting her and their kids to this daily uncertainty only prolongs their trauma, and I think the oldest daughter never reconciled with him because she was the only one in that family who saw things as they really were and that is a clue telling us that most likely the change didn't last.
One can only hope that couples who end up in such a toxic marriage both learn something so that these patterns are not dragged into their future relationships. Most abusers like this are narcissists who can never really be "cured." The one being abused has to go no contact, experts say, in order to move on with her life. It looks like the woman was sucked back in and if it was a true story I doubt that none of these behaviors reoccurred. It's more likely that for the sake of publicity they made an agreement not to air any more of their life, but that the man continued to slip up behind closed doors. We viewers may have been misled about what the real outcome of this relationship was. We only know what they allow us to know.
To move on the abuser needs to consciously decide not to abuse his next partner. It is less likely that he will go on to have a healthy relationship than his former spouse.
The one who was abused needs to learn to love herself enough not to go back into that subservient role, to recognize the signs that a partner is toxic, and to have the courage to be alone rather than putting up with cruelty just to "have someone". She must be very clear on her limits and that if that line is ever crossed again in her next relationship(s) be willing to back up those limits with action and get out early on. Maybe with someone new for the one abused trust can be established but only when that person proves trustworthy. Blindly trusting based on someone's word alone that you don't need to fear just repeats the pattern all over again. His mistress had the right idea and clearly was emotionally healthier than his ex-wife. She had her own business and life separate from him and understood that her autonomy was too important to throw away for some man. Many women don't leave, go back, and stay in horrible conditions for 15 years because they lack the belief in themselves and deep down think that it's too late to become independent, so they find it easier to just go back to the only life they've known no matter how miserable it might be.