Obc non creamy layer clarification

Hi I'm a UPSC aspirant and I'm trying to get my OBC NCL certificate to avail reservations. However the tahsildar refused to issue me an OBC NCL certificate saying that my father's salary is over the income limit. Even though his salary income is over the limit, he works as an assistant sub inspector in the police department who was appointed as a constable into the department about 25 years ago which is well below the class 1 of class 2 fears of officers. Now I know that the income from salaries and agriculture income should not be taken into account while considering the NCL status of an applicant, for some reason the tahsildar ( who is supposed to have knowledge about this) has no knowledge of this. To tackle this I filled an ITR asking for clarification on whether the income from salaries should be taken into account, but the reply I got was that "The question I am asking involves interpretation of rules which the department did not indulge in" and this turned out to be of no use. It is clearly mentioned in the office memorandum that the salaries of income and agriculture should not be clubbed while taking annual income into consideration but the tahsildar does not seem to know the definition of clubbed. Can someone help me with this? Can someone suggest me any other document that I can use as proof or a count ruling that I can show to the tahsildar to convince him? Thanks in advance