Man, you keep going on the passports. Within the US, parent can keep a child's passport/refuse to allow a child to be taken out of the country, but that's not the same for withholding the passport of another adult/spouse. There's an argument for theft. There are probably cases to be made for other crimes. And I don't even know if there are passport-specific Fed laws about it in an expat situation. A quick trip to the embassy/consulate would fix that, anyway. But why do you keep bringing it up? If she's left, he didn't. And though there are requirements for taking a child out of the US without the other parent's consent, I'm going to say that a parent escaping an abusive situation in another country to return to the US isn't going to provide any cover for the other spouse withholding the passport.
TL; DR: withholding your spouse's and/or child's US passport to prevent them from returning to the US would be a fucking bone-headed move.