I am so sorry for your loss. Putting our babies to sleep is one of the most difficult decisions that we can make. We know in our hearts we are doing the right thing and we don't want them to suffer, but our intellect screams something so totally different... In the end it's always the right decision for them, just doesn't always feel that way to us.
I know what you mean when you say that you can never own another Yorkie.. When I lost my dog (he was 10 years old, not a Yorkie) I said I'd never ever own another dog for as long as I lived. I got too attached, and letting Freeway go was the hardest thing I have ever done. I felt like I let my vet kill my baby, and to this day I hold my breath anytime that there is the smell of rubbing alcohol in the air, as he smelled of it afterwards (and I get allergy shots once a week, so that's a lot of breath holding). He died in 2005 and I am just now feeling like I can share my love with another furbutt again. I feel like he would want me to, especially now that I am ready. I hope one day you feel ready as well, it's obvious from your post that you loved little Toby with all your heart and the world is full of dogs of all kinds just waiting for that kind of love.
RIP Toby...
