You should sit him down and talk to him. I don't mean to be mean, and I apologize if this comes as a bit insensitive, but this seems primarily like a relationship issue. You already seem to know everything, that it's not a good financial situation to be in (you seem to have a child you're taking care of and taking on loans so you can both have the child taken care of while you work and pay the bills while he struck out at OCI, is now doing DA work but doesn't seem to like it, and it's uncommon to go from DA 2L summer to biglaw, plus I don't know of any federal clerkship that is still accepting apps to start in Fall 2018). If he has a lot of loans, it's going to put even more strain on the family. So you NEED to talk to him about this. I don't care if he feels bad and gets defensive. Make sure you're open minded and let him know you're there to help him in any way and you're in it together, but don't let up on confronting him about this. Don't let him just bury his head in the sand and all of a sudden you're in a bad situation cause he's too prideful to tackle the situation head on.
Here would be my strategy:
(1) perfect app materials and mass mail to firms asap, and have a good story ready to tell when asked why DA 2L summer
(2) mass mail apps to federal magistrate judges. Their hiring timeline might be slower and it's an easier clerkship to land.
(3) mail apps for state court clerkship, maybe a state supreme court clerkship will pop up
(4) if he's open to public interest, try that.