My husband doesn't take care of his son (my step). I have to be the primary caregiver. What should I do?

You're clearly the efficient, organized and committed one. The boy is very fortunate to have you in his life. I imagine that once your talents became clear to the man in question, he gladly stepped back and let you take care of things. Would talking help? Counseling? Blackmail? Just kidding. Good luck with this difficult situation.