Hi and welcome to this part of the site Frustrated
sounds to me like you made a good decision based on prior incidents, your sons well being and ultimately your own well being.
going no contact has clear benefits for you and it may indeed help him too.
Leaving me to clean up my own mess was one of the things that eventually got me sober.
You ex has the same resources available to him as everyone else
If he does drink, it's REALLY not your fault - it just means he hasn't go a strategy to deal with life yet that doesn't include drinking yet.
D