Hi J.-
I would retain an attorney. It is expensive, but it is worth the money. The attorney will help you create a uniform child support order and also a visitation order.
Your attorney will be able to advise you of how to legally handle the situation of your son's father's drinking & visitation. There is no need for you to stay during visitation, or be at your son's father's "beck and call" in arranging last-minute visitation. There is supervised visitation available through the court system. I have the feeling if your son's father is not seeing you/trying to control you through visitation, the visits with your son will stop altogether.
The best/easiest way to get child support is if there is a wage assignment on your son's father's paycheck. The money will be deducted from his check and direct deposited or mailed to you. If he is in arrears (which I'm sure he is), they will give you his tax return and after that they will take his driver's license, after that they will hold him in contempt of a court order and incarcerate him until he pays his support.
This is going to be a long and uphill battle for you. Your son deserves to be supported. You also deserve to be supported through this process. Getting an attorney will give you the most information in the quickest amount of time and will bring order (and hopefully resolution) to your situation.
Finally, when your son's father contacts you about the child support and visitation issues (which he will) refer him to your attorney and/or the court. Tell him you are unable to discuss these issues with him. Don't get into arguments that go nowhere. For this alone, the attorney is worth the money.
Good luck,
T. Y
SAHM of four (9yrs, 7yrs, 18 months and 22 weeks pregnant with baby #4)