Oh you poor, poor thing, Inelegantly - listen, there are the three magic Cs of alcoholism that people who live with alcoholics need to learn, understand, and absolutely repeat to themselves 200 times an hour.
You did not CAUSE it
You cannot CURE it
You cannot CONTROL it
Of course you feel terrible when he cried. You love him, you care about him, you want him to be happy.
By contrast, what he loves is what he chose: the drink
Now, on what planet does "I chose to be gambling and alcohol over our family. Now you must give me primary care over our vulnerable son" sound like the response of a rational, loving parent?
What he loves is the drink.
What he thinks about is the drink.
What he values is the drink
What he's chosen is the drink.
It's your job to protect yourself, and your son, from someone who has chosen the drink instead of you both
He might dry out.
He might never stop drinking and gamble himself into serious debt.
He might end up in a gutter hugging a bottle of furniture-polish and then suddenly see the light, then spend the rest of his years a reformed man.
You will never, ever know while you are enabling him drinking and gambling.
You can only do what you CAN do: get him out of the house, stop/freeze/close all accounts that are in your name as well as his, and start talking to solicitors about access, maintenance, and divorce. He's chosen the drink and the gambling, my love - and his addictions are going to get worse before they get better (If they ever get better).
So, so sorry this has happened to you. Now you need to be a bit ruthless, for you and your lovely little boy's sake.