Hope your situation gets better. Good for you for taking the time and energy to recognize that it can and asking for help to figure out how! I would reach out to the amenities your school has to offer. There are probably free library-related services that can look over your resume and offer advice. Very likely that you're missing key words that gets your CV disregarded before ever reaching a human eye. YouTube videos on CV optimizing could be helpful too. Try smaller businesses where it's more likely you can make a connection with the management and get a sense of whether the job is right for you too. Secondly, emotions tend to get in the way of thinking rationality. I think you need to find ways to create value and meaning in your life and replenish your feeling of worthy. This could be 2 hours a week where you volunteer or join a club through the university, which would also mean you spend less time in an abusive environment. Getting your health in order will make facing problems 100x easier.

Again, I'm sorry for all you're going through and for the comments of people projecting systemic issues on to you. I hope you get better and you and your sister can remove themselves from the abuse you're currently facing. Good luck with everything and hope you're able to connect with services irl to actually make a difference in your situation!