My senior dog has kidney/liver failure, vomiting blood. Can he live?

Poor Bruno! I can see the brown material in his vomit and the very dark stool, which is likely digested blood. This happens because acids build up in the blood when they are not filtered by the kidneys, these acids are very caustic to the tissues of the stomach, and result in ulcers, which bleed. The prognosis depends on the cause of the kidney disease, as certain conditions can be treated and managed for some time, but unfortunately, the prognosis is typically poor to grave. Bruno likely needs fluids to prevent dehydration, and medication to protect the lining of his intestines.
The kidneys are also responsible for making a hormone, erythropoeitin, which helps the bone marrow make new red blood cells. Along with the gastric bleeding, this is causing the drop in hemoglobin.
The decision is not easy, but humane euthanasia may be an option to consider for Bruno, as kidney failure is known to be painful and very uncomfortable in humans. Unfortunately, treatments such as subcutaneous fluids and toxin binding agents such as Azodyl and Epakatin are palliative at best. I am happy to answer any additional questions you may have.