I'm so sorry for your loss. There is nothing more difficult then being there with your pet as they pass on, especially when it's unexpected
As a vet tech student, with limited clinical experience, I can't tell you whether bringing him in would have changed the outcome. He would have been put on fluids and had a CBC/Chem run. Maybe they could have extended his life for a short while, but with everything that he had going on it may not have been for long. A lot of what we know in vet med can be directly related to human medicine. If an elderly person comes into your hospital w/ liver disease, kidney failure (75% loss of kidney fxn, is that the same in human medicine?), anorexia, vomiting, possible neurological behaviour, skin discoloration, and what appears to be decrease peripheral perfusion (possibly linked to the existing anemia), what would you think?
Your training in a medical profession will make this harder for you, but will help you at the same time.
Stop doubting yourself, you didn't do this to your dog.
You did an amazing job of caring for him, and you were there with him.
As for the sudden blindness, glaucoma usually accompanies cataract so that may be a cause.
The antibiotics that are given slow iv are typically done so to prevent hypotension or anaphylaxis. The load on the liver wouldn't change as the dose is the same either way.
To end my post, again I will say, stop blaming yourself. It's not your fault.