That's not low miles for a csc failure.
Plenty of people here have had it with less than 5k miles. One guy had it fail on the test drive of a new one.
If the csc needs to be replaced, so does the master. There are HD versions of both available. Swapping out the flywheel to a lighter one piece one is a major upgrade, and it'll never be cheaper to do than while the trans is out.