The top tier airlines your husband is targeting don't use recruiting agencies in the ordinary sense. Their recruiters are their own HR employees and communicating with them may be difficult. I'm not sure what the former FAA employee was suggesting. As far as I know, none of these carriers will convert a foreign license...they just don't mess with that stuff...because they don't have to. Legions of qualified pilots are storming the front gates.
I do know Delta will sell your husband an ATP-CTP course allowing him to take the FAA ATP written exam...for about $5K. That's about as far as they'll go to my knowledge. It may get his application reviewed but without an FAA license, that's about all one can expect. If I'm mistaken about this, someone will correct me.
You might check to see if each airline has a Facebook recruiting page where people like your husband ask questions. I know Delta has one...not sure about all the others.
As others have suggested, checking the regionals to see if they'll help your husband is a reasonable option.
Good luck with your efforts.
Last edited by bafanguy; 7th Aug 2019 at 19:30.