Oh my, I am so sorry for the pain you are feeling in your loss of your Toby. 17 years, not to mention half of your life must make it so painful for you. But you are right in also feeling relieved and happy (in a way) that Toby is now free from pain and from the suffering of his seizures.
R.I.P. sweet angel Toby
........and hugs to you. I hope your heart heals in good time, and to getting another yorkie????? Never say never; someday another little one may capture your heart and need you to love them just like Toby did.