Yeah it's possible the new line was installed wrong and started leaking or the line itself was just a bad new part and started to leak fairly quickly.
The coolant hose is hard to say, not likely that the heat of the PS line did anything as that fluid shouldnt get that hot to melt the rubber. A rub through or just an aged hose could be the reason for the leak.
As for the missing oil on long trips, these cars are very well known for buring oil. The motor shuts down to 4 cylinders on and off all the time at freeway speeds depending on engine load and rpm etc etc. The cylinders that aren't firing let oil past and it burns up when those cylinders become active again. Some say different brands of oil may help burn less oil but overall it is a common issue with the early 5.3's in those cars. GM says a quart per 1,000 miles is okay but that is still alot.
A solution to that problem is to disable the AFM/DoD feature so it cannot switch into 4 cylinder mode. That would be something only a tuning software could do.
