I am sorry to hear about Doris's problems.
The pink skin tag that has tripled in size worries me. It may not be just a skin tag. The best way to find out what it is and if it needs to be removed would be to do FNA, fine needle aspiriation. Your veterinarian would insert a small, hollow sterile needle into it, to get cells to look at under a microscope. If abnormal cells are seen, this should be removed before it gets any bigger.
The same with the hard lumps on her shoulder blades; I would do FNA to find out what they are.
The rash could be related to the growths, or could be an allergic reaction. You can apply some Cortaid or Cortizone 10 ointment to the rash. Giving Benadryl might also help: 25 mg 2 to 3 times a day if she weighs around 25 pounds.
Spinning on her rear could also be a sign of allergies, and the Benadryl might help. I would also have her anal glands checked. The glands might be impacted, inflamed or infected and need to be emptied, or she might need antibiotics.
The raised sores are also a concern. In addition to the antibiotic ointment you could try the Cortaid I mentioned above.
All of these could be due to an allergic reaction, but I would want to check and make sure that the hard lumps, raised sores, the rash and the angry red skin tag are not some kind of skin cancer. I would have her checked out by your veterinarian as soon as you can.
Let me know if this is helpful and what other questions you have.