I recognize that this response is late, and that I absolutely cannot speak to experiences that are PhD specific, however I am interested as to how OP ultimately handled this, and in the event that the situation is still unresolved or someone else looks to this question for an answer I may be of some assistance.
First of all, is it at all reasonable to abandon your chosen field of study or completely upend your life because someone is "unapproachable?" I hope that anyone who is pursuing a terminal degree would say no. My approach has always been that professors are available to me whether they like it or not, and I have yet to have this belief invalidated. A major commitment associated with a position in academia is teaching and interacting with students, and while it may not always appear this way, this commitment is likely what drew the professor to academia in the first place. One of the most enriching academic relationships I have developed is with a professor who is absolutely the most unnapproachable and stand offish professor within the college. He regularly tells students that the world needs t-shirt salesmen, destroys incorrectly formatted homework in front of the class, and unilaterally refuses to answer any questions related to problem sets to give only a handful of very real reasons he has earned this reputation. However, I have found that well formulated questions can be utterly irresistible to his teaching sensibilities. Additionally, he is absolutely one of the staunchest advocates for student rights that I have encountered. He labors intensively to foster the environment he believes is most beneficial to the students who will actually carry through with their study in the field, whether it is because of him or in spite of him. I can guarantee you that any student who would transfer or quit because of their interactions with him are not the students who he spends time benefiting.
Often times people are not hard to approach because they want to be that way, humans are social creatures. That being said, be selective in the manner that you do approach some people. Some professors are receptive to a student establishing a dialogue through a "simple question" while other professors, like the one in my example and I am inclined the one in your question, believe that a student has more to gain by investigating simple questions on their own, especially considering that you are pursuing a PhD in mathematics. My advice would be not to approach the professor with simple questions, you will gain far more from answering simple questions on your own, after all a very valid problem solving technique is breaking down a complicated question into easier component questions, and recognize that if you absolutely cannot answer a simple question on your own it is because it is really a complicated question that the professor may be more willing to address when posed as such.
Most importantly, I really hope that you DO NOT leave or abandon your chosen field simply because you see someone else as an obstacle. It will never pay off to hurt yourself in an attempt to hurt someone else. If you have a well formulated question ask it and if the professor doesn't like it then fuck him (new to the community I will edit this if the f-word is frowned upon) be persistent enough that he realizes that it will be easier to help you than to belittle you, but recognize that you are being held to a standard which requires you to answer questions on your own if it is in your power to do so, and realize that if you demonstrate to him that you see the value of his time and only make use of it when necessary that he will likely be far more receptive to you requesting his time. Ultimately, there will be people in your life who ARE INTERESTED in making your life worse and actively work to do so. My experience has been that these people do not have PhD's and have not spent their lives making far less money than they could elsewhere educating the next generation, but even if that is not the case, it is past time for you to decide whether or not you will allow them.
