What should I do about my dad who is verbally and emotionally abusive to my mom on a daily basis?

What should I do about my 81 y/o Dad who is verbally and emotionally abusive to my 83 y/o Mom on a daily basis? Here I am again, a year later and the verbal and emotional abuse that my father is giving my mother continues. It had gotten a little better for several months and now it is getting bad again. He has her in tears almost every day. Recently, she bought a ham from the store. He told her (not in a nice way) that her she should have bought cabbage to go with the ham, "Don't you know that cabbage goes with ham?" he asks. So she goes out the next day and buys cabbage and makes ham and cabbage for his dinner. He won't touch it. She tells him, "I made you ham and cabbage." He ignores her. Now here it is 4 days later and he still hasnt touched the stuff. He's previously told her if she doesn't like it she can just leave - this is between two 80+ year olds, married 60 years next February!! Mom has to watch tv in the bedroom cause he dominates the living room tv -- all day long. If the phone rings and he doesn't have it by his chair, she has to get up (with her walker) and to answer it even if he's closer. He's constant making snide remarks to her and she's a nervous wreck most of the time. She tries to hide it whenever I call. I wish I could stop in every day, but unfortunately I live 500 miles away. I've told her to talk to her doctor about this, but he goes with her to the doctor. Should I report this "elder abuse" ?? If I write a letter to her doctor, do you think that will be any good? I don't think Dad would ever intentionally hurt her physically, but he's making her life absolutely miserable and I'm afraid it's going to start affecting her physically. I live with my own daugher and grandchildren, so I cannot move her in with me and I can't afford to quit work and move to their state. Any suggestions would be appreciated.