Oh my heart feels for you and your little (grand)girl! You must get her and yourself out of there. Here are some suggestions:
1) Get a part time job for the hours while she is in school. Perhaps the school might have something for you? You can explain your absences to your husband by tellin ghim you are volunteering at the school as a teacher's aide or something.
2) Open a separate bank account to deposit your pay checks in.
3) See a lawyer to make sure you have ducks in a row as to assets you may be entitled to.
4) Make sure you pay A LOT of attention to your granddaughter. A lot of the abuse she is receiving may be mitigated if she understands that the two of you are in this thing together. By a small TV and an extra comfy chair for her room, and spend your evenings in her room with her.
5) So her stepmom won't have her? That stinks. 10-12 is far too young to decide a child is beyond hope. And it's stinky on the part of her Dad that he has so obviously chosen his new wife over his daughter. That is a wound that will be a long time healing for her. That said, if she is to live with you, you need to ensure her dad is paying a consistent form of child support. Ask him for help in moving out. Threaten to go to court to get a formal CS order - see how stepmommy likes that!
6) In the long run, I'm hoping you will be entitled to a good chunk of the land your husband bought with the money from the sale of your house. And that he will not be able to touch your pension.

Note: Do not let you age dissuade you from seeking employment. My MIL has been singing that tune for 10 years now (she's 69) and it is NONSENSE. My husband has a small business, and our best employees have been/ are seniors. They are the most reliable, professional, skilled, updeat people we have working for us. Many small and large employers are wising up to this.

Good Luck