I'm considering leaving my husband because I can't stand his elderly Mom. Am I wrong?

My sister in law, that lived with my mil, died in February of this year so we had to move in with my mil. She's 80 years old and can't live alone. I believe she has alzheimers, but she hasn't been to a doctor for years now so she's never been diagnosed. My mil refuses to bathe and I'm disgusted by this! She has a little dog in the house and it's never been house trained so it uses the bathroom all over the house, and she claims she can't see to clean it up. The "I can't see" line is used every time it's convenient for her, but she sees just fine! The "I can't see" line is also used every time she uses the bathroom and leaves her mess all over the toilet. She doesn't want us to wash her clothes! This place stinks! She sneaks around a lot, goes through our stuff, and takes things out of our bedroom. We've had to install locks on our bedroom door and my 16 year old sons door to keep her out.The biggest issue is the dog. I hate that dog! We try to get my mil to eat. but she wants to give it to the dog. We buy steak, cut it up for her, and she gives it all to the dog. We go buy her a Sonic burger, she takes 2 bites and gives the rest to the dog. Everything we give her, she gives to the dog.My husband has told her to stop, but she sneaks and does it anyway. She's doesn't want to eat anything but sweets. She's going to die and we will be blamed, but we can't get her to eat! Let me say, before we moved in here, I cared a lot for this woman, but not anymore. We have been here for about 7 months now, and I've never even sat on her furniture because it's too nasty. We live in our bedroom, because we can't stand to be in the front of the house. I go to my mothers house to cook our supper because I'm disgusted by the smell here. The absolute worst part, the part I have cried myself to sleep over more than once, is I have a 2 year old little boy that's being raised in one room. We can't let him go into the living room, down the hall, or in the kitchen because of that nasty dog. When we 1st moved in I kept the floors swept and mopped because of the dog using the bathroom. But I could sweep and mop and 5 minutes later there's puddles of dog urine. I decided the dog didn't need a clean floor to piss in. My husband or mil cleans up after the dog, and I stay back here trying to entertain a 2 year old. I'm so tired of these bedroom walls. I've begged my husband to send her to a nursing home, but he says he can't until her mind is completely gone because she's always told them to never put her in one. Everyday I think about leaving, but I don't want to take my son away from his daddy. I know I sound like the bad guy in all this, maybe I am, but I can't take this. I'm suppose to make sure my kids grow up in a clean environment and now I've brought them into this hell. What do I do? Do I leave my husband? Do I keep pressuring him about the nursing home? Or do I just keep living in this bedroom, for possibly another 5-10 years, and wait for life to be normal again?