Yes, Hawkeye is right, the local women's shelter will not only provide good support, they can help you find out what assistance my be available for you and your son. You may be eligible for some kind of housing and food allowance, but a quick call can let you know all about that.
Now this suggestion may or may not be good, but it's worth thinking about. Since he sprung this on you and he wants out, perhaps he can provide some financial support for you and your son as well. If you ask him to sit down and talk about the housing situation and your plan to leave, he may just do that. Since you are the lease holder and you said he makes decent money, would he be willing to move out and continue to pay the rent for say six months? Something along those lines. Barring that, he may just need to stop being so hostile and understand that you are stuck there for a little while longer. This is all of course if he will talk about it. It would probably be unwise, if he will talk, to bring up anything about the ending of the relationship or the relationship in general - he will probably end the conversation then. I KNOW it will be hard, but think of your Son and yourself and your well being. Perhaps think about it like a business meeting.
He needs to understand that right now you have nowhere to go with your Son and hopefully, maybe, he will do something decent.
But yes, please call the women's shelter as soon as possible, it will help you feel more in charge of what's going on, there is help for you.