Your husband has issues which he finds hard to deal with. he's about to lose you, which is probably also going to be hard for him to deal with. He has choices. He must make those choices and be prepared to live with the consequences. Neither choice will be easy.
In the meantime you have a son who needs stability and support. He is your highest priority. Your feelings for husband will understandably have to take a back seat in order to help your son. Life isn't fair.
I hope husband can see that he can make it easier on himself as well as you, but the ball's in his court. I do hope you can make it work, but right now if husband won't deal with his problems, how can he be equipped to help you with your child?
You may just have to both be content with a long-distance relationship for a while and see how that goes.
You can't change husband, any more than you can change your son. But people can adapt and choose to make changes in themselves, especially if they are positive, healing changes.
Marg