You are wrong, sorry. The correct answer is NO: the sentence is grammatically wrong. The sentence should read: "If I were queen, you'd be my king."
You use the singular, "was," for indicative modes of expression, i.e., where you are stating facts or asking about facts. For example, "I was in the office yesterday" or "Was I in the office yesterday?" You use the plural, "were," for subjunctive modes of expression, i.e., where you suppose something that is known to be false. For example, "If I were a rich man."
You are wrong, sorry. The correct answer is NO: the sentence is grammatically wrong. The sentence should read: "If I were queen, you'd be my king."