Hello! I am just seeing this thread. I'm sorry for all you are going through with Tobie. My yorkie, Layla, also has invertebral disc disease, however she went down quite quickly and lost the use of her back legs totally. She had surgery and didn't recover any feeling. She had another flare-up, but in her neck, about 7 months later and we treated it conservatively (crate rest and medications) and she recovered fully.
I just want you to know that many dogs do get better conservatively, without surgery. Surgery is really hard on their tiny bodies, and if they are kept still enough, even a slipped or ruptured disc can heal without it. A lot of people just think surgery is the only option so I wanted to let you know that conservative treatment can also be quite successful (and much cheaper!) Dodgerslist is a website (and yahoo group) that has helped me a lot as a resource for IVDD. You can check it out if you want some information and people to talk to who have all been through it:
Dodgerslist Home Page
You and Tobie are in my thoughts!