all he has to do is be there for our child but he doesn't!
That's not a simple request for an addict, unfortunately.
I think you need to trust your gut, from your post, it sounds like your gut is screaming to you that this is bad, that he is still using. Like the above poster said, even if he is not, what he is/is not doing is not acceptable and it is putting YOU into a bad place.
You setting up the job fair.... If it was important to him to work, He would be LOOKING for a job, not placating you by going to something you set up.
From what you said, he's twisting things to justify his behavior, manipulating you.
Everyone has their limits. I can tell you from getting out of a bad marriage many years ago, with a child, It was FAR better to rely on myself than to hope and beg for help from someone who was not willing to/able to give it. Far less disappointment and anger.
Keep talking about it, I swear it helps. Trust your gut. Too often we don't.