lots of blood

For future reference always carry hemostats. You can clamp off a artery or a vein & stop the bleeding. I had a catchdog who had his jugular cut. We clamped it off & made it to the vet & no problems.
I am curious about your vet that says he could not do any more. Any dog that loses that much blood, either needs a blood transfusion or some fluids put back in. I would have changed vets right there.jmo
Also if you can get some ringers, you can put the fluid back in a dog yourself. This is really good for heatstoke. If not that, you can always shoot water under the skin.