I have a great deal of sympathy, particularly in the circumstances you're talking about, for women or spouses who find themselves in that situation. Having practised family law for 30 years, I dealt with those situations far too often, and I certainly would never jeopardize the ability of someone to raise the issue of self-defence in those very difficult circumstances, but I don't think your amendment is necessary to achieve that.
You do need the “reasonable” in all the circumstances. You do need both a subjective and an objective test. In the history of our jurisprudence in this area, I think that balance has been achieved. You don't want to tip it into a situation, in my view, in which an unreasonable perception—one that anyone would see as unreasonable—could be taken as the norm or the standard.
We need to allow the courts the discretion to look at all the circumstances. I have no doubt that the individual perceptions of a person in such a situation—more often a woman than a man—are taken into account and need to be.