Thank you for posting this response,was waiting for one w/experience to respond!
Hello and welcome. I agree that's quite a lot of beer, and eventually it will all catch up to him in serious health issues. Retirement is a tough one. I'm 68 and retired. We go from a daily purpose in life to nothing much to do.
You wrote "I want to be able to motivate him...": I have a daughter who is in and out of drug recovery. We, as loved ones, are powerless over controlling the people we love. It's entirely up to them to finally find what ever it is, that spark of the Devine or burning bush, that will give them the desire to finally stop using and take the necessary action to stay stopped. We want to turn screws in their head, but we simply can't.
You wrote "do you think he can taper off his drinking safely?" Sure he can. If he decides it's finally time to stop, a visit to his doctor to make the call on how to go about it. (Alcohol withdrawal raises blood pressure somewhat.) Millions of alcoholics have safely stopped and are enjoying their retirement with meaningful lives. I'm one of them.
I suggest that you try Al-Anon meetings, because his drinking has been effecting you to the point to where you posted here. Look up the main site and see what it's all about. I've been going for years. It helps me to not be alone while watching my daughter destroy her life.