Your husband is incorrect. The Federal government is noted for its lengthy and meticulous criminal investigations
, and they spin a wide web. I cannot tell you how probable it is that he will be charged, but I can tell you that the fact that they have left him alone for now is without meaning.
The Federal government is fond of cases with lots of co-conspirators and they don't make their move until they have all of their ducks lined up in a row. In general the statute of limitations on most Federal offenses is 5 years, and they could take every day of that and will if necessary to secure a conviction.
I don't intend to scare you, but your husband had some involvement here, even if it was innocent. That makes him a potential suspect. He should secure a lawyer if the Feds contact him again with any more questions. He's within his right to say that he wants to speak to an attorney before discussing anything further. The government knows all about Miranda rights
and they can't hold that against him.
Meanwhile, although he might be tempted to tell this story to others who know about the little old man, your husband should not discuss what he did to help him with anyone other than the Federal Criminal lawyer he ultimately hires if necessary.
Right now, no attorney is needed He has not been charged, and they are not looking to interrogate him further. If that picture changes, he needs a lawyer. If he doesn't know where to find a local Federal criminal lawyer, he can contact his state bar association's Lawyer Referral Service.
They charge somewhere around $50 for the referral which includes a half hour free consultation with a lawyer.