Cat over grooming, not allergies

My 10 year old cat has been ripping all of her fur out for months now. The second i remove her cone, she starts aggressively grooming and pulling out chunks of fur with her teeth, to the point that she gives herself scabs. I have tried multiple strategies- allergy and anxiety meds (Apoquel and Gabapentin), hypoallergenic food (Purina proplan hydrolized duck, which she refuses to eat anyways), unconventional protein food (both duck and rabbit, she has now been on RAWZ rabbit food for like 3 months?), and nothing has worked. Aside from that, I have put her in sweaters, but she finds a way to either pull them up or tear holes she can tear her fur out through. When she wears a cone, she usually has trouble using her litter box without getting poop all over her paws, so she usually starts peeing/pooping on the furniture after a few weeks. After taking apoquel for 2 weeks with no progress, I asked the vet if they could increase her dosage, and they told me that the only way they are willing to do that or prescribe something else is if they can run blood tests, x-rays, and perform a bunch of other exams that i absolutely cannot afford. At this point she has been on Gabapentin for 4 days at 12.5mg, with no change whatsoever. I am feeling so defeated and upset that she is still so uncomfortable despite several unhelpful trips to the vet. Are there any other steps i can take to address her itching?