I'm with Janet. The fact that you have problems and questions and feel like you can't discuss it with your teacher is more of a concern for me than the grading business itself. I also suggest heeding the other fellow who said to look for warning signs that your dojo is cult-like.
I would check into the dojo's parent organization and the source of his credentials. If he is completely independent and/or self-appointed, then his ranks may not be worth anything anyway, except in-house. If my investigation into my own reluctance to communicate with the teacher and of the school itself turned up anything fishy, I would look around the area for a dojo with more legit credentials. If there are no such Aikido dojo, I would also consider other arts. Aikido isn't the only martial art in the world.
Finally, wherever you go, don't discount your idea of training with no regard to rank. I have gone that route, because I found that my own thoughts and feelings about testing had little to do with what I like about doing Aikido. The only problem it has ever caused me is occasionally seeing far less experienced but higher ranking people get to lead a class or something, which isn't much of a problem. I'd rather just train than worry about the pecking order. The other "problem" was moving and traveling to different dojos where I couldn't wear my Hakama. I had some emotional attachment to wearing it and I had to buy new gi pants that were presentable as outer-wear.