"It's just that if I find half a bottle of vodka that he's hidden, I can't help myself. I certainly couldn't give it back to him!"
Why not? It is his bottle, after all.
I hope you don't mind me banging on about this but it's a sign of how much this is having an effect on you.
You've become embroiled in a battle of wills against an addiction and, as a consequence, are losing touch with both what's normal and also what's realistic. This is one of the big issues with being in a relationship with an alcoholic - you have to actively work very hard to keep your feet on the ground and not get swept away by the repeated crises and drama.
Addictions are not amenable to reason. You can't win against his addiction because it is not in your power to do that. All you can do is decide what is, and is not, acceptable behaviour from someone you are choosing to spend your life with.
By doing things like pouring his booze down the sink you are turning what is his problem into a battle between you and him. You are doing senseless, pointless things because you can't help yourself. Now do you understand why people call alcoholism a family disease? The craziness is infective. You feel driven to do them because you have become so embroiled in his drinking that you have lost track of where you end and he begins.
I was in that position. It drove me nuts. Seriously. I became obsessed with my ex's drinking, I kept copious notes of how much she drank and on which days, I checked through the recycling and counted the wine bottles, I poured it down the sink and I rooted through the house to find the hidden stashes. It was insane behaviour that absolutely dominated my life. I ended up in A&E on more than one occasion because the stress got so great that I thought I was having a heart attack.
Al-Anon will help you to let go of attempting to control his drinking. The tools they will show you won't be about talking to him more "effectively", it will be about how to stop his problems from continuing to dominate your life.