Help Me Please With My Dog! 10 points?

Ok this will be quite long, I have a pembroke welsh corgi, I have had her for about 8 years and in all this time I have spent on vet bills along 6 thousand 3 hundred and 80 dollars on her. She inherited mites in the womb of her mother, so these mites are just not really curable as those on the surface of the skin. She has just developed a huge mite thing again she has huge patches of fur gone on her bag her paws are eaten raw with no fur. Her skin is black and brown and red not pink at all!! not even in the ears her ears are all bloody and so are the bald patches. I have tried 10 different pills fromt the vet, 12 different capsules from the vet, 4 hot spot medications, horse linament, non wheat food, 3 different ear meds, tea tree oil, doggy lotion, flea and tick color, drops and shampoo, etc...... I have just recently spent 500 more dollars in vet bills for what she has now. I cannot afford anything else anymore, she is not getting better it never ompletely goes away. I love my dog but I can't help her any more. I am trying one last thing from a nearby vet but it is the last thing I can do. Also she has gone to eight different vets to find a solution. I am done, it pains me to right this, I am crying just sitting here typing this but I can't do it any more. What do you think I should do put her down, try to sell her to someone that could help her, I really don't want to give her to the humane society. And the thing is she doesn't act sick she just bites, scratches and yelps alot cause her paws are so tender and swolen. Pleas help!