Kaaawa, welcome to SR. Good for you for seeking information at this very crucial stage of your relationship. That is a very healthy thing to do.
There are a few alarms bells in your post, but for me the relavation that he hasn't had a drink for 25 years isn't one of them, apart from no mention of any recovery-type work (like AA, therapy, SMART, church programs etc). There is nothing wrong with not drinking alcohol. One alarm bell for me is that he recognized that he suffered from depression all those years ago and his sole method of dealing with it is by sleeping for days. Has he had therapy? Does he manage his diet? Does he exercise? Does he have any insight into why he has depression?
The addictive-type personality revelation, though, is the key for me. He is telling you who is with that quote and also with the sleeping thing. It could be a test to see where your boundaries lie. A fait accompli - I am going to do things that aren't healthy for me or for you and I have told you, so it is your fault if you stay wth me and the poop hits the fan as a result of some addiction related incident (drinking, gambling, pain pills, whatever).
I may be wrong, but I would advise proceeding with extreme caution and at a very slow speed. (I actualy, I would say run away because life's too short, but I know it's not always as simple as that.) You need to keep an eye on his actions, not his words, whilst making sure you don't give more than you have to lose until you have more information of just who he is. I would also be interested in his reaction to you stating that you need to take things slowly.
How did the conversation come up, just out of interest? And why does he have alcohol in the house if he doesn't drink it? Why the mention of Listerine? He's right that it contains alcohol - my ex used to drink it for the buzz and the smell-covering properties. Actually, there's another test for you - he's laying the ground for you smelling alcohol or Listerine on his breath.
Just my thoughts based on the few hundred words you have written. I may be very far wide of the mark, but I hope to have given a little food for thought. There are some great sticky posts at the top of the forum if you want to read some more.