How individualized is the MPC reasonableness standard? Even in MPC jurisdictions, juries are asked to assess battered women by a reasonable person standard, right? So does MPC's reasonableness standard essentially only adjust for age?

At least under NY penal code, which takes the same possession as MPC for self-defense I believe, the standard is a reasonable person in the actor's situation. It is a mix of an objective and subjective standard, and the defense can submit evidence that goes to: Physical movements of the potential assailant, Any relevant knowledge the victim had about that person, Physical attributes of all persons involved including the victim, the victim’s prior experiences

The victim's prior experiences is the line-drawing prong, where it is not clear which evidence is admissible.