Wow, that is quite a story. Bless you for taking her in. Sounds like she has a phantom tail, like people have a phantom limb.
The OCD stuff is tough, once it's firmly established in their brain, which it clearly is for your dog.
Have you tried anything outside of the box for her like acupuncture (if that is available where you are), Bach flower essences or calming aids like Melatonin? I bet there is a homeopathic remedy that would help too, if you could find a practitioner.
Ruth & the 4 Legged Rescue Gang
Rafi the malaroo
Gio & Varda, the krazy kittens
....In my heart: