Hiding and lying are part and parcel of alcoholism, flower. My A hid his drinking from me for YEARS. Even after I finally learned what was going on, the signs of him being drunk were subtle. An outsider would never have had a clue....
He also hid his cigarette smoking from me for years. Every so often, he'd get sloppy and get caught, then swear he was quitting but in reality hide and lie about it yet again.
With both the drinking and smoking, I asked him to please do so openly so at least the dishonesty wasn't present. It didn't happen. The secrecy is simply part of the disease. People have said it's b/c the A can't admit to him/herself the truth of the matter either; maybe that's true.
I'd be willing to bet that what you've seen, what you know about, is only the tip of the iceberg. That was certainly what my experience was.
As far as talking to him about it, what do you hope to accomplish? HE is aware he is still drinking; YOU are the one who didn't know. It seems he is telling you pretty clearly what he intends to do, even if he's not saying it in so many words.