How do you set up boundaries with an ungrateful, rude mother-in-law who is out of touch with reality?

My husband and I had to move his mother in Feb 2011 due to her falling in Dec 2010. After moving her in and looking at her behavior before we moved her in I realized that she had some SERIOUS issues. She wants to sleep all the time, not bath, exercise or eat unless you nag her. She does have hypothyroidism and depression but even before she had these issues she was not a clean person. When she is sick she will vomit in the floor or go to the bathroom in the floor making no effort to go across the hall to the bathroom. She makes awful comments to me that I am "holding her hostage" "a drill sergeant" "mean" "a dog hater" (because we do not let her dog stay inside during the day-our 14 yr old son has a cat that hates dogs and she has tried several times to let the cat out of the house resulting in hours of us having to look for him). She will not take her medicine unless you stand and watch her do it, we also have to keep hidden any other meds because she will take them whether they are hers or not, she snoops in our bedrooms especially mine and my husbands. We had to install a double keyed deadbolt because if we leave the house and leave her home she will try to put mine and my son's two cats out because she thinks if she gets rid of them then we will let her dog stay in 24/7. We completely redid a room for her, her dog comes in the house in the evenings and stays in her room all night (we do make her put him in a kennel to sleep because he potties on the carpet due to her not letting him out when she lived alone), she has her own tv in her room, her own phone line with a separate number, we swapped appliances to make it easier for her since she has a hard time bending over. I am her main caregiver as I am a stay at home mom, however, I never realized that I would be getting a 2 yr old trapped in a 71 yr old body. I was the one who suggested we bring her home rather than leave her in an overpriced nursing home where she was not getting physical therapy after her fall. I set up therapy for her in our home but she was unwilling to do the work she needed to do so she never completely recovered. She lies to my husband about my son and I but instead of him saying "mom, let's be honest" he sympathizes with her. Some days I go to my dad's after I take my son to school because I hate to go home, but I can't stay long because I never know if I am coming home to the cats being let out, powdered milk all over the house because it was spilled and she walked all in it, tea bags all over because she spilled them and figured I would pick them up. But she acts like I am ugly to her. I know I am having burn out and I have recently developed high blood pressure (I was not at risk for it before her) and I am seriously contemplating going on antidepressants. Some days I just sit and cry because I am so upset that this is my life now, I am 38 and most days I see no relief in sight, I see myself being used up to care for this ungrateful rude old woman. We can't put her in a home, she owns a couple of rent houses that the rent goes to the mortgages that she and late hubby #5 thought would be a good idea. I have tried to talk to my husband but he always acts like it isn't that big of a deal and I guess since he is gone at least 8 hrs a day 5 days a week it isn't, he is an only child so there are no siblings to share with. She has a sister who lives about 4 hrs from us who has taken off work before and let us bring her there and if we lived closer she would help us out more but that just isn't possible. When I have asked my husband to talk to her he will say things like she isn't like you, I can't talk to her about stuff because we don't talk about stuff. I have even contemplated my son and I moving out for the summer, not sure how we would manage that.........I did contact an adult day center the next town over but they charge $62 per day, she has no money left to pay for it and my husband in a police officer so we don't have a lot of extra either and I don't think I should have to go to work to put her in adult daycare. She does not have dementia, or Alzheimer's and her current doctor that found the thyroid problem doubts she has depression, he thinks all her issues have been the undiagnosed thyroid but even after being on meds and getting the thyroid regulated she refuses to change her behavior. My dad has depression and a thyroid disease also so I am very familiar with both of them together and what to expect. She tells us all the time to let her move home where she can stare at the walls and not bathe if she doesn't want to. Any advice is appreciated. Am I just being ugly??????