Sorry for your loss.
Back in 2005 or so,we lost our 6-year-old yellow Lab,Sunshine..to bone cancer.
(We-meaning my mom,dad,and me.)
I was there with the vet when they put her down.
I cried nonstop for 3 days.(yes,even at work.didn't care who saw me,as the emotional pain was too much.)
Your dog looks eerily like Sunshine did.