With Washington Irving’s word choice "Old Scratch must have had a tough time of it!", he says that Tom Walker didn't get along with his wife. In the story, the author descrives Tom's wife as a tall termagant, fierce of temper, loud of tongue, and strong of arm. And it says that they often had conflicts.So, with the phrase "Old Scratch must have had a tough time of it!", Tom actually commiserates the devil aka Old Srcatch.