Errors, regrets, and pain

I have never done this before so please forgive me! I lost my precious Hope, and 8.5 year old rott/lab mix, last week. She was a huge physical and emotional presence in our lives and we miss her desperately. The circumstances of her loss make it so much more difficult and recovering is not foreseeable. Here is my story:
Two weeks ago today, Hopey was seen as the vet and diagnosed with osteosarcoma in her left hind leg. It was in the early stages, her lungs were clear. She had been dragging it around for some time; we thought it was arthritis which the vet had actually diagnosed her with just a few months prior (with an x-ray).
Being that she was still so young, we opted for amputation, then two rounds of chemo – THE GOLD STANDARD – and hoped for some more time with her. I had researched and read many blogs, websites, that my plans and hopes were feasible.
Here’s the sad part and the part that I cannot live with: the surgery lasted 5 hours. Wednesday 12/14 3pm-8pm, my dog was under anesthesia. She was not extubated until 3am. I did not leave her side throughout all of this. She would not wake up with the alertness that a dog should, and when she did wake up for brief moments, she screamed out in agony. All this time, I watched, I prayed, but to no avail. On Thursday it was decided to transport her to a vet hospital. They did everything they could to relieve her pain and although they succeeded in making her comfortable, stabilizing her vital signs marginally, they did not recover her mentations. it seems obvious that she suffered from oxygen deprivation during surgery.
I made many huge errors here and hope that others will learn from them.
1: I trusted my vet – never again will I get only one opinion.
2: I should have known to go to a larger facility/hospital for the procedure.
3. I should have listened to my first instinct with the initial diagnosis – take her home, treat her palliatively and when the time was right, put her down.
I do understand the consequences of that decision – extreme pain, possible pathological fracture; however, Hope was still playing, running, jumping, eating, and happy once she had some tramadol in her.
I am not left with the huge dilemma of having to seek legal action? this will not return Hopey.
or deal with what happened?
talk to my vet about what happened? Vent my anger and disappointment.
ask them to accept blame and pay the bills?
None of the above will bring her back. I have learned many lessons from this – that is all I can walk away with.
On top and above my own issue is that my daughter is a tech for the vet and assisted in the surgery. My relationship with her is prime over all else.
So, to wrap it up, I am left alone in a dark place to deal with immense sadness, guilt, and shame.
I do not know how to recover, I do not know how to stop the pain. I do not know how to let my Hopey go.