OP I was the woman putting up with this, the drinking, the moods, anger and violent outbursts. I too did the begging for him to stop drinking. I too accepted that four cans was better than eight. I too hoped things would get better, because I thought there was no way I could leave. Things did not get better, the drinking never improved, the aggressive violent outbursts got worse the more I challenged his behaviour so I left. It was hard, really hard, and the prospect of careing for a child on my own scared the bejesus out of me. I did it though, and thank god I did. Unfortunately I left it too long to stop DS having visits with his father. I didn’t know the magnitude of the violence and emotional abuse he was perpetrating against our son until it had already been happening for a long time, and even though I acted as soon as I found out I’ll never forgive myself for letting it happen. The fall out is so much worse than you can imagine, and my son doesn’t have SN.
Re the four cans not getting him drunk, this is not a saving grace, believe me, because he’s an alcoholic, he drinks to get drunk. Alcoholics are not like you or me, they don’t drink because they enjoy the taste, or because it relaxes them, or even because they want a good time, they drink because psychologically, and probably physically judging by the amount you say he used to drink, they need alcohol. It’s a dependency, and when they feel they’ve not had enough they’ll have more, and the more they drink the less it is enough. There is nothing, and I mean nothing you can do to change this. Conquering an alcohol addiction is incredibly difficult, even when a person desperately wants to, because the drink is central to their existence. Their mind is constantly wanting drink, figuring out where the next drink is coming from, planning the next drinking opportunity. You cannot influence this, not even if you try really really hard. The only way you can influence his drinking is to show him that his actions have consequences, and you have to follow through, otherwise there’s no point even trying.
I suggest you do as PP have suggested and call Women’s Aid. Take it from someone who’s been there, this situation is far more serious than you think it is and things will not improve for you, or your son.