The practical application of the laws surrounding domestic disputes, restraining orders, domestic violence, etc. are a fucking train wreck. The central problem here, imo, is a lingering, very sexist approach to presumptions about who can and cannot commit domestic “violence” (abuse, battery, etc.). Most human beings will still presume that the “weak” female is the victim, whereas the “strong” male is the aggressor - it takes a lot of direct evidence to counter this.
Procedurally, as well, as has been noted upthread, there is an extremely intangible presumption that the “first-to-file/complain/call spouse” is the victim. This is primarily because the perceived costs of an erroneously finding in favor of the filer is minimal - oh, ok, the abuser has to go live at a friend’s place and they get a court record - when compared to the perceived costs of erroneously finding against the finder (they wind up dead).
Adjudicators (cops and judges) will view the “victim’s” evidence with both wide-angle and narrow focused lenses; if the particular incident doesn’t give meet the definition of “abuse”, most people will fill it in with the back story. If the particular incident meets the definition of abuse, then no amount of back story can ever explain or justify the incident (and I’m not talking about physical threats here - verbal sparring back-and-forth can easily form the basis for many restraining orders).
Unfortunately, this is a reality that has been crafted from years of experience - in most of the cases dealing with domestic abuse/violence, the “sexist” paradigm holds true, and in most of these cases, the victim is telling the truth, even without trial-level evidence to prove their point.
But, to answer the op: I am not in favor of an expansion of affording an expanded basis for justifiable homicide based upon “battered women’s syndrome” - there is no imminent danger that needs to be met with a legal right of self-defense. Some posters have analogized to hostage takers; I would seriously question the applicability of the affirmative defense of self-defense if you were in a hostage situation where you could successfully flee without drawing the attention of the hostage-taker and you decided to go and “kill the bastard” just because he wrought harm on you in the past.
Self-defense as a legal concept ought not to sanction vigilantism masked as a type of “yeah, well I really need to make sure I can get away” justification.