What is the ruling regarding a husband telling his wife: "If you pluck anything from your eyebrow hair, you are not my wife, and I don't know you," if he intends it as a threat and intimidation, and then the wife proceeds to do so?

Allusive divorce does not take effect unless the husband intends to initiate it. Your statement to your wife, "You are not my wife, and I do not know you," falls under the category of allusive divorce. Since you did not intend to initiate divorce but rather intended to threaten, nothing is binding on you, even if the condition is met.