Marriage counseling please?

My wife and i have been married for 23 years; we have a 21 year old son who graduated from LSU yesterday (BioChemistry major), and a 16 year old daugher who will be a high school senior next year. My wife and I have probably argued more than the average couple (I guess), but I always thought we would be together forever. I've never believed in divorce when there are children involved, unless there were circumstances such as infidelity, or abuse, or things of that nature. About 5 years ago my in-laws moved to the town where we live, about 15-20 minutes away from our home. Since then the relationship between my wife and I has progressively gotten worse. I place lots of the blame on my mother in law. She has always been able to persuade my wife to do things for her that she didn't want to do; like go to her class reunions, go to funerals, go to weddings, and now, go to the store for her. It was always something I tolerated, but now that she's living near us it happens all the time. She's healthy, she's just a lazy ***. And now my father in law is having health issues, so she is relying on my wife more. My brother in law lives an hour and a half from where we live, and he is never asked to do anything because he has no problem just saying "HELL NO" when he is asked. My wife doesn't know how to tell her mother no, to anything. I few months ago my wife told me that she was thinking we should consider a divorce, but that her mother suggested to her that we should wait until the summer time, when our kids would be done with this school year. Since then we've been to counseling, and I've been as nice as possible. But for some reason my wife is meaner and more ugly to me than ever before. I'm feel like she is in a situation with her mother where she knows her mother wants us to get a divorce, and she doesn't want to tell her mother "NO." Her mother knows that I don't care for her, and that's only because she takes advantage of my wife, and now she does the same thing to our son everytime he's in town. Also, with my father in law's health declining, I wouldn't put it past my mother in law looking for my wife to take care of her if he should die soon; that's how she thinks; she is evil and selfish. Well, I'm at a point now that I can't take anymore of the rudeness and disrespect that my wife dishes out to me everyday. But remember that I don't believe in divorce, and I hate to think what it would do to our kids if we were to divorce. Does anyone have any suggestions as to what can be done here to help us get through this? I've heard of something on the religeous side called Retrouvaille, but I haven't met anyone thats tried it before. Help please.