I am so, so sorry. Continue being the strong woman you obviously are and keep on hugging and loving your little boy.
Your husband needs to get himself checked into a program pronto or he shouldn't be allowed visits with his son. Maybe that will be a wake-up call for him or maybe not. Certainly the family court would find this behavior to be dangerous to your child and suspend these supervised visits until he is sober.
It is his loss in the end. I know that your heart breaks for your son, but it would be breaking even harder if he had to continually witness his Daddy inebriated and stumbling around. Kids are smart. They can feel the tension in a room. They know when something is not right and when Mommy is upset.
Just keep your eye on the prize, which is your little boy. Continue to make him feel special and try as hard as you can to keep him separate from this situation and any anger and resentment you feel toward his dad. Luckily, he is only 18 months and might not understand why Mommy's mad, but eventually he will and he surely feels the stress and anxiety associated with Daddy's addiction.
Are you attending any Alanon meetings?? It might help you see that this is his struggle and his alone.
So sorry. 8(
Peace.