I disagree with Roy regarding the control of the circumstances by the step-mother, and that is why the OP should contact Texas Adult Protective Services. Financial Exploitation of a Vulnerable Adult by a Caretaker is a felony in most states, and probably is in Texas.
I wholly support Roy's advice regarding a concealed carry. It is sound advice.
I don't think the law considers a spouse as a caretaker. A spouse can set someone out on the porch, bag and baggage. Clean out the bank account, sell off the household items and either borrow money on the home place or sell it and disappear into the night. Isn't marriage great?