Alright I haven't been in an abusive relationship myself before, so this is my opinion and you can ignore this viewpoint if you want.
I believe the man can defend himself without ending up on the wrong side of court or how people view it. If you are a real man, you have the ability to let the woman understand when something has to stop, WITHOUT having to ever hit her. If it is in the moment, you can block the attack, much like you would do in a fight with any guy. Most importantly, you will have to stand up for yourself and let her know this has to stop.
I have found in the past, if someone hits me once, and I don't want to hit the person back because it is someone I have too much respect for, I warn the guy once in a very serious and body language, that if it happens again he will end up on the other side of MY attacks. Whatever it was, this has worked more than once, and I am pretty sure it will work even on crazy woman, but you have to get that understanding over, that you will not give a damn about the consequences that may follow your inappropriate action when you hit the person back. You will be surprised how the situation changes, and the person will respect you for that.
I can just imagine how effective this will be if you warn the person you will hit her back, infront of your friends, because then you have witnesses that you did warn her before hand, and they will possibly be on your side and get a chance to explain the situation.
When in a difficult situation like this, I think you need to control what people think and then act.
Either way, like I said, this is my opinion, I have never had a woman abuse me, but I know how to deal with men, and I will apply the same principle if I have to, to a crazy abusive woman.