Today Spark has gone to sleep for the last time. The vet sedated him first, and he slipped into a slumber really quickly, less than a minute. The actual passing was painless for him and I felt his spirit leave. I asked the vet if he'd gone at the exact moment that he did leave.
I hope that he's now a doggy angel, and is pain free.
It will take some time for me to stop feeling so upset, although I am weeping, not crying.
Thanks to the vet for making Spark's passing as gentle for me as well, and thank to my three children and Becky, for helping me get through this. I think my ex is even a little upset that Spark has gone.