Since your dog seems to have a history of atopy (licking and chewing paws and the spot on her back), the lesions on your dog's ears may be secondary to (atopy) allergic skin disease. Common causes to what you describe include: sebaceous cysts, histeocytoma's, or fly strike (fly's biting the tips of the ear and causing infection).
However, due to her age I must also list much more serious causes i.e.: skin cancers, which include: squamous cell carcinoma, mast cell tumors, or other skin cancer. Cancers increase with age.
If the lesions are histeocytoma's each lesion will usually resolve on it's own in 3 months, but she could get other lesions in other places. Sebaceous cysts can be drained but they will continue to fill up again unless you have them surgically removed.
If there is a possibility that the lesions could be skin cancers, it would be best to have them completely excised and biopsied.
is it expensive to have the sores biopsied? how is it treated?Is it fatal?