Oh mama, that sounds heartbreaking. Your poor wee boys! Sending them big hugs!
He needs to sling his hook! Being a parent is a privilege not a right! I wouldn’t have them go back overnight, tbh I wouldn’t want them to go back full stop.
They have you and that is enough mama 
Document 
everything
I would take him back to court and request supervised visitation. Or no visitation at all.
Take him to court. Meanwhile, send them with food. Like I know, it is a no-no, but don’t let the kids go hungry.
Do not let them go period
If the kids can coherently tell you these things, they can also tell the courts. You know what you need to do, just do it. For them.
You say THEY. How many is THEY? And still you BOTH can’t get your shit together.
Three sides to a story.
She says. He says. And the truth.
Dont send them there.