Jess, my father was a committed and dedicated alcoholic for at least the last 20 years of his life, and it wasn't really the alcohol which killed him (tho' obviously, it compromised the treatments he had for his lung infections over the last couple of years).
I know that my mother tried to control his drinking towards the end, but they just argued about it all the time, it was THE most important thing for him when his ability to get out and about left him.
If your father really wants his drink, he'll get it, whatever you try to do. My dad used to go with my mum on her supermarket trips. He'd sit in the car outside, with his oxygen mask on, and get passers by to go in and buy half bottles for him, of course my mum knew nothing about it. Some of the satisfaction was, I think, getting the better of us, but it meant he had a secret stash which my mother knew nothing about, and could top himself up when she refused him. After he died, my mum found several empty bottles hidden in his clothes in the wardrobe!!
You need to ask yourself if the alcohol is doing THAT much harm, in the light of his other health problems. Do you want to spend the rest of his life arguing with him about it. Think about what gives you pleasure, and how you would feel if it was the only high-spot in your day, but everyone around you tried to stop you.
Believe me, if we could live my dads last few years over again, we might do it a bit differently. Look in your heart to decide how you want to deal with him.