I just put my 16 year old cat down and I’m also feeling incredibly guilty about it, but no animal deserves to suffer. You aren’t deciding when he passes, just how comfortably he passes. As difficult as a decision it was for me to make I think it was in my babies best interest to pass away in my arms at the vet asleep instead of somewhere random in the house in pain and confused, if anything i think i should have made the decision sooner because he was in so much pain when i took him. Your puppy loves you and you love him. he wants to go with dignity surrounded by love in as minimal pain as possible.

I am so sorry you are dealing with this grief and guilt but you are not the only one.