Should I relocate to take care of my mother?

I live in one state and my mother lives in another. In the beginning of 2010 my sisters and I began to notice a change in my mother's memory. This was not your average memory loss due to age, it was more serious. Well, at the end of 2010 one of my sisters passed away and it was detrimental to my mother's mental health. The passing of my sister seemed to perpetuate what was already going on. My mom was diagnosed with dementia and she seems to be regressing rapidly. She has a husband who wants to control everything and is undermining. She met and married him when we were in our 30's and they've been married for 20 years now. He went to her boss and caused her to lose her job and has taken away the keys to her car. He did this without conferring with her or us (her adult children). He doesn't keep us informed of what is happening to her. I think that this is his way of controlling her. My sister and I just recently found out that she leaves the house when she is upset (she doesn't get lost or wander around). He is also very jealous of the relationship that she has with us. When I talk to my sister who lives in the same town as our mom, she tells me of the changes that she's noticed and it really makes me sad to hear how she's changing so fast. It's like I've lost my sister and now I'm losing my mom. We've always had a very close relationship and she tells my sister that she really wishes that I could move to where she is. The problem is that I don't have the funds to move to where she is or a car and my sister can't take care of her because she has her own health issues and her husband isn't looking out for her best interest or welfare. I'm at a loss because I really want to be with her so that I can take care of her. I can't move her here with me because of her husband and she has said many times before that if she ever got sick that she did not want to come back to live here. I just don't know what to do at this point.