The thought of loss can be a really strong motivator.
The best thing you can do right now is to be open, honest, and not accusatory with him.
Make him read what you've just written, though perhaps not the public version (that would cause him to hurt and become defensive).
Don't gripe at him, don't scream, don't get mad -- become resolute and talk to him.
After you've let him know where you are at, he will either change and make progress, or he won't and you'll have your answer.
If you think he's salvageable, then you need to have a serious discussion with him -- but NOT an argument.
He is the only person that can change his behavior - if you try to make him change by using subliminal language or 'hints' or indirect comments, he won't. A lot of men don't pick up on some of the mental games played by our female counterparts (ya' know, the "yeah but if I told you what I wanted, you wouldn't have thought about it first!" deal lol)
But seriously, this is something you cannot fix from the voice of the public because on one hand, you'll have a lot of women that will come at you with "JUST LEAVE HIM!" and their "rah, rah, female power" voices, but that's often not useful advice.
Then you'll have some guys who will try and blame YOU for it "Yeah but what did YOU do!" type of comment.
And others will claim he's having mental struggles and should seek counseling -- which may or may not be true, but this is something HE will need to come to terms with.
But to get him to that point, you have to be willing to walk away. You have to be resolute. He has to understand that you are on the last straw and he has to believe that you will leave because you don't feel he's holding up his end of the relationship.
If you sit him down and do all of that, and he STILL won't participate in the day-to-day, then you won't have much other choice than to separate -- if you're to the point where it is causing your life to struggle, and causing harm to your child, then yeah, it's time.
Leaving is a last resort, but it sounds to me like you're there.
