Did mum and dad consider pursuing the debt legally? If they went through a legal process to recover the money, they might be able to discover more details about the 'divorce', might even dig up (so to speak) more shady stuff that had been going on.
Like so many lucky breaks Chris Dawson got, the family retreated into painful isolation, Chris had convinced them Lynn had left her children, they were humiliated, and broken with grief..
As far I am know, they let it ride , taking on the Dawsons, with their 'moral superiority', a man left to bring up 2 kids alone, left in the lurch by an absconding wife, ( divorce then was still a bit on the nose ) , they had no where to turn, and up against Peter Dawson, meant they could be in court for years paying a barrister, Chris got his for free.