With that in mind I'd be confident in saying anywhere from 50-60% LF's will be turning a profit for them
You have got to be joking! If the front end isn't filled then that sort of load factor will result in the service lasting the season, and no more.
Look at US Airways and PHL-BHX. Loads were great, yields apparently less so, and the service last one season - and only the high summer season at that.
As usual, it's not load factor that drives a service it's yield.
As for cargo; on a 757 - forget it as a major revenue earner. it's a totally different animal to the B777.