Given to their own devices, men don't want to grow up. When my first was born, my husband hung out with his friends a lot. However prior to kid #1, he would go out with the possibility of not coming home because of alcohol. (He is English, and would never consider drinking and driving.) The first time he used the "I may not be home if we're drinking" line, I let him know that this was not acceptable. What if I called him with an emergency and he couldn't come. Sorry. If I have to grow up, so does he. With the addition of kid #2, he understood how much work it was because he actually was involved more.
As far as the cleaning, I have a friend whose husband is totally anal about how clean the house is. They have 4 kids and I know she gets totally frustrated with his expectations. He does help out though. If he is going to have those sort of expectations, than he should help out and not go out.
Okay, I know he is out already, and I just want to caution you on the whole on/off relationship because of the instability it offers your son. And you did not mention if he is planning to still be involved in your son's life even though he is gone. My friend is going through a messy custody thing right now, so I know how all-encompassing that can be.
The biggest thing I see here, is the thing that most couples have to deal with once the kids arrive. That is--not forgetting that you are a couple once you have to take on the needs of a kid. It's classic--the woman focuses on the needs of the new baby and the man doesn't know where he fits in, so he goes off and finds his own thing to do. Sometimes it's just hanging out with the guys, playing incessantly on his computer, hiding in his workshop, having an affair or whatever. It isn't the woman's fault. It's a problem of logistics. Everyone has to do their job, and communication is key.
Sorry if I rambled. Hope some of it helps. Good luck. Take care of yourself and your son above all else.