My wife and I both studied in ba'al teshuva institutions. We both learned that as a married couple, the husband should be responsible for making Torah-related decisions and the wife should be responsible for making decisions pertaining to the household, which are no less important. However, my wife keeps questioning whether what I say is right, and constantly wants me to ask a Rabbi. I feel that I don't infringe on her sphere, and she shouldn't infringe on mine. So I insist that she accept my opinion on these matters, which I think she should respect. Could you please help me explain this to her?
This question should really be directed to, and answered by, a rabbi who knows you both, knows your situation, and whose opinion is also accepted by you both. So I can only address it in a general way which I hope will be helpful not only for you, but for others as well.
The fact that you are asking this question to a rabbi is a good thing – it shows that despite your reluctance to consider your wife's position, you're at least asking what troubles you. That should enlighten you as to her need to feel a rabbi is consulted regarding what troubles her.
You see, what you write that you both learned in your respective institutions is only generally and partially correct.
First, marriage is a joint venture in which all decisions affect both people and therefore neither has a monopoly over any sphere. Rather, they are to work in unison such that the specialization of each does not preclude his or her involvement in the sphere of the other.
Second, it's not that each is necessarily responsible for making the decisions in the relevant sphere, but rather responsible that correct decisions be made. As in all areas, this often entails consulting an expert.
What gives the husband more of a say in the “Torah sphere” is that men have more of a requirement to study Torah, and therefore generally have more familiarity with it. And since women are generally more knowledgeable and experienced in matters relating to running a household, they are given more of a say in that sphere. Accordingly, neither one's say is arbitrary, but based on an assumption of knowledge. But if either questions the opinion of the other, he or she is certainly entitled to consult an expert.
In the case of a husband whose opinion in Torah-related matters is being questioned by his wife, he or they should consult their rabbi. The husband should not feel offended or threatened, but rather be willing to ask what the Torah says. Either way, it's to his advantage. If what he said was correct, he gains respect from his wife. If it was not, the fact that he was sensitive to his wife's concerns and humbly sought Torah guidance is also appreciated and respected by his wife.
Of course, if a wife is constantly, unjustifiably questioning her husband, or alternatively, rightly questioning but in a demeaning manner, she has to work on improving herself, and that's a different discussion. But in most cases, her "opposition" should not be viewed as harmful, but rather as a fulfillment of the verse referring to one's wife as a "helpmate opposite him".