When are you going to get out of this toxic situation, where people are excusing an 18-year-old for "just being drunk"?

BTW, true feelings don't come out when you are drunk, people can become a completely different person when drunk, especially alcoholics. But focusing on how awful he is to you when drunk is a red herring, it's just you being in denial of the terrible situation you are allowing yourself to live in.

Maybe if you called it quits that might be a wake-up call for your wife. If not, you'd still be doing yourself a huge favor. It's impossible to be healthy living in a situation like this.

Why do you end up engaging with him when he is drunk.  TBH, I would cut a wide path with him on this.  He would find himself alone in the livingroom/kitchen talking to the coffee pot.  Sure, it's your home too, but when you know standing next to the hammer will get your toes hit.. why do it?

And Tog is right.. substances can cause people to act wholly out of character and say and do things they really don't mean.

I was recently watching an episode of below deck  and the boat's captain was sitting by while two of the crew were drunk and behaving badly.  He explained that there was no point in trying to deal with them in the state they were in.  Drunks aren't themselves.. won't listen to reason etc.. So he waited until the next day to deal with them.  

I really don't see any point in engaging with this kid while he is under the influence.. and it does.. to an extent.. take two people to argue.  I understand he may be "starting it" but you also don't need to take the bait and can leave him to his drunken mess.  If he becomes destructive.. call the police.