I want to cry reading your post
First of all it does not sound like you are on the correct medication and/or dosage you really need to see your dr ASAP. Are you seeing a psychiatrist? Is hubby seeking help for his anger management issues? I don't think he should be smacking a 1 year old. Also, your DS may be acting out because both of his parents are not happy. I think you may find he improves when you are both in a better place.
Do you have family who can hep out?
When you say drinking, do you means substance abuse?
Please know that you are not alone!! I had/have PND after my third daughter was born. I couldn't cope, I wanted to explode over the most insignificant things and Cried so much. It was managed through medication and then when I realised it was causing me to gain weight I slowly weaned myself off of it. The withdrawals were horrible and I had what felt like a breakdown when the drug was finally gone from my system. I am still not feeling very good but am slowly improving, I think. You should know that things will get better, but it DS take time and conscious effort.
Please see your dr xxx