Has anyone had a dog with as many issues as mine?

The fact that you are still not giving up on her just means that she's mighty special. How old is she now? It can be due to age or it could be that her genetics aren't as good as mix breeds are supposed to have.

The worst experience I had with my dog was when he was a very young puppy. He had mange which I had no idea how to treat back then because it was my first dog and I wasn't allowed to use soaps because he was less than 3 months old. I tried bearing with it (because that's what the doctor said) then he grew corneal ulcers because he kept on rubbing his face to the cage. Fortunately, I was able to go to another vet who had the solution to all our problems.

It probably sounds minuscule to what you're experiencing right now but I've realized that sometimes researching and reading about our dog's ailment can greatly help. Maybe some of your dog's problems can be reduced or minimized with proper diet. (e.g. my dog's melanoma was greatly reduced after adding turmeric in her dog food).