That is the issue. HE took the loan. The ex walked out with zero debt and a college diploma while he and his wife have to pay for all the loan.
Ok, dude needs to take his ex to small claims court and sue for the money to pay for the remaining debt. Did he have any paper work that she signed during all of this?
Honestly, I doubt you'd get very far taking the ex gf to court, unless she signed something that she would pay him back, or even if there was some agreement. But that does not appear to be the case at all here, at least with what has been presented. Someone buys you something really expensive (in this case, an education) and because he has a hard time paying for it, you have to pay him for your "gift"? That's like, a guy buys a ridiculously expensive e ring, then you break up and he can't return the ring. You don't have to pay him back for his decision to spend that much on you.
I am really bothered that he was asked point blank how much it was and he lied, but still, he made a stupid decision years earlier, and it sucks. But it's not really the ex gf's problem now. And it sucks for the wife that she married a liar.
I am also feeling wrath towards this guy. I'd be beyond furious if I found out that my SO had lied to me about his financial situation. Money can greatly affect a relationship. Having to sell my house and my car because of his blatent asshattery would make me take a long hard look at things, at the very least. Lying about that kind of debt for so long is deceitful and very calculated, not a one time oopsie kind of mistake.