I would try a product like Revolution or Advantage Multi to treat for fleas and mites (which can be hard to find even under a microscope).
She may be having food allergies as well, as chicken is at the top of the list for allergens, try a dog food that uses a different type protein (may need to eliminate poultry all together) or use a limited ingredient diet.
For pups that sunbathe, I'd apply a sunblock to the tummy. The skin is so delicate there I would think some kind of protection would be warranted.
And I would also schedule an appointment with a Vet Dermatologist. With all the scratching, she may need to be on medicine as once the skin is irritated, the door is open for bacterial and fungal attack.
I would also hold off on all vaccines until these problems are resolved. Vaccines do not do their jobs as well on pups whose immune systems are busy fighting off other problems, and can complicate the issues she's already dealing with or cause new problems.
BTW: Welcome to YT!
