Death and denial

I'm certain you did the most loving thing for him.
It will take time, feeling that sadness and loss. No easy thing -- a dog is such a wonderful friend and companion - an irreplaceable individual.

These days, I have the vet come to our place when euthanasia is the only option.
It means they die in their familiar environment with less stress.
It costs more, but it's well worth going without a few basics for a while.
We buried our cat just outside the front door, with a rose and herbs planted over her grave.
I buried my favourite mare in the orchard, with a mulberry tree over her and a memorial photo with the story of her life sealed in glass. She was the mother of four beautiful foals and we shared many many miles of riding the bush together. She was so sweet natured and easy to train, as were her fillies and colts. One of them is now my main riding horse - with such a deep bond.

I hope things go well for your remaining dog.
It's such a sad thing, but it's also one of the noblest proofs of real love when one cares more for their well-being versus suffering more than our own feelings - which, after all, we will eventually recover from.

I wish you well, and respect and honour your choices.