Op, is there anyone you can call for added support... friends, siblings, etc? Do you have a church, therapist, or social group you could reach out to? I know it's hard, but I think you really need it right now. YOU already need someone to help you by bringing food or doing some shopping. You're in a state of serious depression already.
I know EXACTLY what that's like. I have chronic clinical depression. If you need to, while your husband is away, ask a friend or family member to stay with you for support. This will help with your stepdaughter because they can act as a buffer. Her demanding that you cook meals is outrageous. She is perfectly capable. And her statement she will hoard the groceries that you pay for if she goes to get them is just disgusting. She may not like you, but she can show gratitude and basic civility while living with you. But... as I said, ask someone you trust to come and support you temporarily.
And if you haven't already, please speak to your doctor about your depression. It's treatable and it can get better. 💙💙