I have been trying to deal with my mind, too. My AH is 58, has been active for probably 30 of those years and has been a heavy smoker for the same. So, I read the life expectancy for people who make these kinds of choices and the future that once seemed to stretch out so far in front of us is now looking like he's in the final sprint.
He coughs, he labors breathing, he memory is getting bad, he has fatty liver (amazing its not cirrhosis yet).
Lately I've been lying awake at night asking myself the same questions you do, but I can turn them off more quickly now, because I know this is just what must be, simply because it IS, as Byron Katie would say.
I can only live my own life, and today I really know the power of that one decision.
The rest I must give up to my HP.
People die all the time. When I cry out in anger that something stupid like drinking will probably result in a deadly disease and take someone I've spent my life with and still love, I think about all the people I know who died despite doing everything right. People who ate everything right, cooked from scratch, didn't eat red meat, took fish oil--some of them have gotten cancer and died young.
We project our own values and beliefs on what should and shouldn't be. I believe that God made flowers to grow and bloom. Likewise we ALL should grow and bloom. But, if you notice, when you throw down seed, some of it thrives and some if it never does. That's just the nature of things.
So for whatever "reason" we think things aren't happening as they "should," they happen anyway, and there's nothing we can do about the uncle who died running a marathon, or the little kid who got leukemia, or our dear loved ones who seemingly choose to drink themselves to death, leaving us as collateral damage with our guilt and our questions and our deep, deep sadness.
I really wish you peace. I wish myself peace! What I just wrote is what I tell myself in the middle of the night as I'm fingering my rosary beads, asking the mother of God to pray for ALL of us sinners, now and at the hour of our death.