I'm so sorry you and your pup are going through this rotten time. You are right, if you think there may be a chance the letter will make you more upset, then setting it aside for a couple of days and forgetting it to concentrate on your pup, seems the best thing to do.
I know that he's finding comfort in your love and care.
One of my pups recently had a very bad kidney infection, peeing lots of blood, but, the antibiotics DID help her a lot, in fact once they kicked in, she was nearly back to normal in a couple of days. I'm really praying that the same will be for your Oreo.
Take care, and give him lots of hugs.
K
x