OK, I'd forgotten what your back story is--that these people are neighbors with whom you had felt very close and now they are acting "differently" toward you.
What I never got, though, was what makes you conclude that they have alcohol issues. You mentioned seeing beers, you mentioned their talking about not drinking.
Whatever their issues are/may be, it appears they don't care to share those issues with you right now. Maybe they are having marriage problems, or other worries, as your husband suggested.
Here's the deal, though, you can't MAKE someone confide in you or allow you to "help" them or support them, even if you would like to. These people presumably know that you care about them. If they want your help or support, I'm sure they know they can ask for it.
Sometimes relationships between people change, for no reason except that people's lives change. I've had good friends simply grow away from me--or I from them. It doesn't mean I didn't/don't care about them or their happiness, just that our lives have changed and the relationship doesn't have the same place that it once did. Sometimes that can be sad--especially when one person moves on and the other one doesn't understand why.
Still, it is what it is, and the sooner you can get to work on accepting the situation, the less it will hurt. Nothing you have said so far suggests that they were maliciously using you. Maybe they were, maybe they simply felt closer to you then than they do now. Either way, you must work on getting past obsessing over the relationship--that can keep you stuck in unhappiness for a very long time.
Try making some new friends, too--it can be a refreshing new thing to try. Maybe some new activities, pursue some new interests. You can still be cordial and friendly with these people next door without being intimately involved in their lives.