I would agree that AUS-FRA is probably going to be your least stressful experience, even though the business seat on that route is considered outdated these days. Connecting in ORD. EWR, IAD means you wont get as much sleep on the flight anyway. For cruises its probably best to arrive a day or two early, but I guess with river cruises it's easier to catch up with the boat. Consider an expertflyer subscription and set alerts for the routes you are OK with.