Yorkie itching like crazy and 4 vets later we are stuck, has anyone done allergy testing?

Our yorkie Olive is 4 and shes been miserable since around September. Started as just licking her paws raw, now its full body itching, ear infections every 6-8 weeks, and these little bumps that come and go on her belly. Weve been to four different vets at this point including one who specializes in dermatology and i feel like im back at square one.

So far weve tried apoquel (worked for like 2 months then stopped), cytopoint shots (helped for maybe 3 weeks each), a hydrolyzed protein diet for 12 weeks (no real change), antihistamines, medicated baths weekly, and special wipes for her paws. Ive spent close to $3000 between meds, food, vet visits, and the dermatology consult. The dermatologist quoted us another $1100 for proper allergy testing including the intradermal test plus a treatment plan that would be ongoing.

Has anyone actually gone through allergy testing for their dog? Was it worth it? Im not made of money but i also cant keep watching her be uncomfortable. Im honestly close to tears about this. She used to be such a happy bouncy little dog and now she just lays in her bed and chews her feet.

Any advice or just commiseration appreciated.