I keep trying to explain to him that an alcoholic can live to be 50-100; the massive alcoholics in my family lived to be 49-74.
Not true.
I've personally witnessed many a mid-30s alcoholic in his current state die within months. Purging bile every morning, barely able to stay awake, not eating, not drinking water, scrambled egg brain ramblings, aggression, crying, further isolation, dereliction of duties (his "work" in the form of "content"), lashing out and explaining how he "doesn't care" and he's "not drunk", devolving back to his toddler brain, complete lack of empathy nor concern for consequences, the list goes on.
He doesn't understand how liver failure works, and if he thinks the toxins are going to his kidneys, he's right, but that's not what'll get him. Excess bilirubin from fibrosis/cirrhosis building up in the system (yellow eyes, yellow skin, anxiety, lethargy etc) causes jaundice, and all the while severe organ damage all over the body. His "pickled brain" is a by-product of chronic liver failure allowing toxins to disrupt signals in his nervous system. His dead liver tissue will start adding more and more toxins to his system, causing a cytokine storm like none other. If he keeps this pattern up, he's dead in a couple of months, and it will be an extremely painful and miserable death.
Once you get to the stage of not eating, and purging every morning, the clock is ticking rapidly. He either stops right now and gets healthy, or he's fucked permanently and quickly. His emaciated, malnourished body can literally not handle this.
Just a note, and sort of a "reward" of knowledge for you. Do with it what you will.