How to set boundaries and stay sane when MIL with dementia lives in your home?

I have posted on this forum before and have found it very helpful. I am still really struggling with how to set boundaries and maintain my own sense of health after my 89 year-old mother-in-law moved in with us from France about 3 years ago, I had not realized that her functioning had declined to such a significant level until she actually moved in. She had come to spend every summer in California, but was forced to wait in France for two years for her immigration papers to process. It was clear to me on her arrival that she had developed dementia. I was not prepared. My husband is an only son and feels a tremendous obligation to take care of her. His mother and father divorced when he was only 2 years old, and she never remarried. The thought of sending her back to France is out-of-the question, even though my husband seems to finally realize that we took on a much larger commitment than we could handle. He says there is nothing we can do about it and we have to make the best of it. On top of that, we don't have the resources to afford a facility here, plus she does not speak any English. So we are truly stuck; she also doesn't qualify for Medicare for another 2-3 years.

She is a miserable person, who complains incessantly about her health, she is paranoid that everyone is stealing her things, mentions non-stop how neighbors are running a washing machine at all hours of the night (We live far from other houses). Our dinners are the three of us - my husband, myself, and MIL - and the conversations circulate around her family and stories from 50 years ago. She sits next to my husband in the car when we go places together and I sit in the back seat.

I do feel extremely sorry for her. She has macular degeneration and great difficulty seeing. She used to be an avid reader. She has heart trouble. She also is extremely hard of hearing, and does not hear without her hearing aids though she very often refuses to wear them, making it difficult to communicate.

She has asked me to scream in her ear but I refuse. I have chronic daily headaches following a traumatic brain injury, so loud noises aggravate the headache pain. She yells frequently and I can hear her across the house; it is very unsettling and makes me feel like I am on high alert all the time. She doesn't see or understand that I am on the phone and has interrupted me in the middle of important conversations. I now close my door. I have taken her to a myriad of appointments and help her at home with meals, laundry, and other things around the house. I rarely hear a thank you. She has a very controlling personality, and it often feels she wants to be the woman of the house. She will tell me if she does not like the way I am cleaning the floor or that I shouldn't take a certain food item out of the freezer for dinner. She hovers. She is waiting by the front door when I drive up to the house. She gets involved in every aspect of our lives, when we have friends over she is always there. At night, she is on door lock and light patrol, and asks us incessantly if we shut the lights and locked the doors even though we reassure her that we will take care of it. She comes into our room with questions. I just feel that I have no breathing space, no privacy. She complains how she has nothing to do. I have gotten her a wonderful native French tutor for English conversation twice a week. We took her to an adult day care facility but she walked out after 5 minutes and didn't want to go, saying she couldn't see. She only has a couple of teeth so we have changed to a softer diet of overcooked vegetables. She is a smoker, and though she smokes outside per our rules, I still smell the cigarettes on her, in the trash, or when I go out to the backyard. It is all very frustrating.

I am currently looking for employment, so do spend a lot of time at home. My husband has a very demanding job and works long hours. I find the only way to have breathing space is to get out of the house. It has very difficult to find a French-speaking caregiver in a small town. We are working, though, on locating someone so hubby and I can get away on a mini-vacation this summer.

Right now I feel very overwhelmed and resentful. She was a very difficult MIL from the start. My husband and I have our own health issues. I have come to understand that you should just agree with someone with dementia and not argue, and affirm their feelings. I am getting better at not taking her behavior personally, that it is part of the disease. But it's a process.

How do those of you that have gone through similar experiences of having an elderly person live in your home rise above the chronic complaints and find joy in being in your own home that may at times feel suffocating? How do you stop her from COMPLAINING all the time? How do I set boundaries with a MIL who doesn't process things well and who has a difficult personality to begin with? Thanks for your comments and advice.