I am sorry to hear that your cat is having so many problems. My name is Rebecca. I will do my best to help.
Her hair loss, the stuff in her ear and the swelling around her claws could be an autoimmune disease such as pemphigus. Steroids might help her to feel better, and might help this problem.
Going blind and deaf could be old age, diabetes, high blood pressure.
Urinating on herself could be diabetes, kidney disease. Kidney disease can cause high blood pressure and blindness.
So she has a lot of possible problems, and to find out what is wrong and how to treat her might require some testing, and expense. Is she still eating, and drinking? Since you are frustrated for her being like this, and if you can't afford to do any blood tests or treatments, then euthansia might be an option. If she is not eating well, drinking excessively, or losing weight, she could have something that can't be treated, such as cancer, and euthanasia is something to consider. It is a very personal decision; every one feels differently about when to consider it, but if she is this sick, it might be the best thing for both of you.
Let me know if I can answer any more of your questions.