I think the issue fairly stated is whether I, having endured cancer twice, at age 59, am willing to stay in a marriage with a husband who abuses me and has promised to continue for the sake of my family?
And I don’t know the answer.
You stay in your marriage because it has the biggest payoff of all your options. It gives you most control over the family. Divorced you will be splitting holidays. Your children won't abandon their father. They will still see their father and do vacations with him. It just won't include you.
Together your children have no other option, but divorced your kids get to choose.
Plus you may not want another relationship, but I bet my hands on your husband at the very least getting a girlfriend after a divorce. The single women who don't want to spend last decades of their life alone will compete hard for your husband. And as you said earlier, you don't want another woman holding your grandbabies and the only way to stop that is stayed married.