Taken from Quara and from my women's abuse group on Facebook:

Can abusers change?
It is not common for abusers to change. According to one study, only five percent of abusers really changed, in the sense of really stopping both the emotional and physical abuse and began treating the victim with respect: and even then change is unlikely unless his life sustains some major impact -- a large number of people "intervene", or he's arrested or fired, or the survivor leaves. And even those changes are still external to him: it doesn't mean he wants to change -- he just wants to put on a sufficient appearance of change to get his old life back.

The situation will not change unless the abuser changes: it is he, not the survivor or any external factor or any problem in his history, who makes the choice to be an abuser, a controller. And nothing a woman can do will change a man: he does what he does because he chooses to. And for change to happen, he must want to change, and he must respect the survivor, neither of which are unlikely. Ask him nicely to change and he will refuse; ask him not so nicely and he will become angry; trying to make him feel better about himself will only feed his ego and validate his behavior. If he ever had enough respect for you to make the changes, he wouldn’t have abused you in the first place.
All survivors must remember that the "Nice" husband who shows up occasionally was the act he staged for you and your family: the "Nasty" husband who showed up a few months after the honeymoon is the real man, with his mask off. The "Nice" guy is the myth; the "Nasty" guy is the one you're really married to. So waiting for "Nice" to return is like waiting for your favorite cancelled show to return to the air: all that is fiction, not fact.

And what if you force the issue, threaten to leave, get outside help from family or the courts? Abusers are manipulators, and even if he admits there’s a problem, he will still try to game the system. He will try, as always, to rewrite the rules of the game: you must forgive him, on his timetable, when he feels he’s done enough to change (in fact, it may be that you never forgive him no matter how hard he tries, and that is your right no matter what he says). He will try to steer responsibility back on you: “I can only change if you change too, you must help me, you must show more appreciation for how much I’ve changed already!” He may shift from more obvious abuse and toward more sophisticated manipulation. He will try to bargain: “I will give up this abusive pattern if you let me keep this other one – I’ll stop hitting you if you stop hanging around with those friends who keep badmouthing me” (which is a bit like negotiating with a terrorist, and you should never have to trade one form of abuse for another). He will evade and dodge, and if he can’t get what he wants with you, he may just give up and seek an even more pliant victim so he can go back to using all his abuse tools as before.

Some women believe that drugs and alcohol are causing the abuse, and that getting him clean and sober will solve the problem. This doesn’t work either: intoxication doesn’t cause the abuse – although it can make the violence worse – so getting him clean won’t fix the abuse. An abuser in recovery may reduce his abuse temporarily because he’s too busy focusing on his recovery, or he may even ramp up the abuse, but they don’t stop abusing when they’re clean. At best they may curtail the physical violence while keeping up the emotional abuse which can be even more damaging. An abuser will also exploit his recovery, making himself and his recovery effort the center of your lives at the expense of everything else, claiming that he should get a free pass on abuse that happened before he sobered up, or using recovery as a bargaining chip – “by challenging me on my abuse, you’re threatening my sobriety!” -- playing off the abuse against the recovery or vice versa.

He may claim that child abuse causes him to abuse as an adult, but that is not a valid excuse, any more than the "Sorry, I was drunk" excuse. Although some kids who were abused grow up to be abusers, 75 percent of them do not. Being an abuser is a choice.

Remorse, even genuine remorse, doesn’t change the behavior, and remorse itself fades away as he gets used to tuning out your feelings; backsliding is the rule, not the exception, even when they make progress. As long as you’re with him, he believes you’re there because you can’t leave no matter what, and if you leave and then come back, the abuse may actually increase because you’ve just persuaded him that you have no choice. If you leave for good, which is he more likely to do: admit he was wrong all along and change his ways, now that it’s pointless since you’ve left, or find a new victim so he can have life back the way he wants again?

Genuine reform is very unlikely in abusers who are self-centered, which describes most of them. And reform is even less likely as time goes on – as the years go by, it is harder for you to pull out and he knows it, as he slowly wears down your self-esteem, drains your energy, separates you from friends and relatives who can support abuser is following a plan that can take years. Longterm batterers are less likely to change.

Once a relationship starts moving toward violence, generally it is permanently damaged. Abusers who are not yet violent will probably become physically frightening even if they don’t shift to outright violence, and the few times a violent abuser does reduce the frequency and severity of the attacks, it’s because the victim is so terrorized that all he needs to do is growl and she cowers. And unsurprisingly, abusers who batter their partners even before marriage don’t stop after they’re married.

There is a small minority of abuser who only abuse on isolated occasions under great stress, but the commoner variety is the “career” abuser, wherein abuse is part of his personality. And significantly, the better-trained a family evaluator is, the more likely they are to diagnose a batterer as a career abuser rather than a one-timer.

Therapists have tried teach couples to signal each other when they feel tension rising, then take a timeout or two, or write out their frustrations, or call a therapist or other player to intervene; they have tried strengthening the positives, role playing, playing back tapes of arguments. But even when abusers get into therapy or other programs to change their behavior, it seldom makes a difference. Generally it is not common for therapy to make progress unless there is long-term therapy (which abusers resist) and/or when there is jail time or the threat of it; inevitably there will be backsliding, efforts to put the responsibility on the victim to make it all work, and efforts to game the system.

Couples counseling – to include marriage counseling and mediation – is extremely problematic because (a) it reinforces the abuser’s argument that it’s partly the victim’s fault, and (b) it give the abuser information which the abuser can use against the victim. Another form of therapy that can backfire, is the therapist who encourages the abuser to vent his feelings, thus validating the idea that giving free rein to his anger is acceptable.

As with everything else, abusers use therapy and batterer programs to game the system: they seldom change their behavior even after completing the programs, and the abuser often tries to use the program to continue control over the victim, asserting that the program is all about how she needs to support him, and trying to use the program to con her into returning home.