Yeah, I would get a transmission expert, preferably Honda trained, to diagnose it.
Could be belt, I suppose, or could be clutch(es), or who knows what else.
At 100K miles, how many times have you (and when was the last time you) changed the CVT fluid? I know you said it was "due", but is that because you just thought of it, or are you keeping to the recommended schedule or better?
2 hours at 80 shouldn't really kill a transmission. Especially at highway speed (which is probably pretty constant, unless you have lots of hills and traffic tie-ups - sorry, but I don't know the highway in question).
Also, if your brakes are dragging even slightly, after 150 miles at that speed they would definitely heat up and drag more (meaning that the drive train would have to work a lot harder to keep speed). That might explain why city driving is no issue. Just a thought.
One or two CVT failures in thousands of cars, and we all jump on the "rebuild" band wagon. I'm not so cure that is warranted. Be careful about posting in panic. If it gets diagnosed as a tranny fault, then let us know. But I'm sceptical.
Good luck with it, in any event.
SOME SAY, that when he gets into his car, he plugs the IMA cable into his left ear … but no one can tell who is charging whom!