An aircraft carrier has many levels of protection. I do not think that NK can sustain, or damage an aircraft carrier to any large extent.
China and Russia have been at providing intel on military movements and placements for a very long time. Nothing new there. An aircraft carrier is very hard to hide these days. Besides the point is for NK to know a carrier is near.
I agree that it would be good to unleash Japan, the problem is that it will take many years for that to happen even if they and we started today.
Japanese Military has very high levels of quality. 1 percent of the Japanese budget is a bunch of money, particularly considering that veteran's pensions and facilities don't count toward that 1 percent cap.
There is a balance between forward deployment for show the flag and effectiveness, and withheld deployment for survivability. I trust our military professionals to make the decisions to strike the right balance. There are a bunch of unclassified old studies by Albert Wohlstetter on that. He found that rear basing was superior in deterrance against a rational actor, and based on that, the B-52 long range bomber was developed. With Kim Jong-Il the assumption of a rational actor may not be valid.
The Saratoga, (our 4th carrier at Midway,) had to be scuttled after the Bikini atoll tests. It was completely impossible to decontaminate it.