How do I help an anxiety sufferer?

My partner is an anxiety sufferer, from what he has already told me this has been caused by his parents not being very nice to him during his childhood. (Apparently his Mum also seemed to be suffering from some form of anxiety or depression too during that time.) Consequently he was not taught to cope with everyday life successfully, and has struggled all his life. I seem to be taking the punishment from him for everything everyone has ever done to him, especially his Mother, who he will not confront about his upbringing because she also suffers with her nerves and he would not wish to be responsible for her downfall. He regularly accuses me of having affairs, tells me that I should not answer or argue back as this makes him worse, says I am not supporting him properly, and in his worst states calls me all the names under the sun. I started out sympathetic to his condition (when we eventually fathomed out what he was suffering from), but now, 10 years down the line, I can feel my sympathy wearing very thin, and sometimes I feel I may be heading in the same direction. When he is calm, he is the nicest man ever, and he is constantly saying sorry to me for what he puts me through, so he does recognise that he has a problem. I just want to help him draw a line under his past and get on with our future, because I do love him to bits, I just don't know what to say or do any more. I do argue back, as some of the things he says are horrible, but maybe this is wrong of me. Also he has been asking me the same questions for almost the whole 10 years, is this a part of the anxiety? Can someone please help me?