But my dilemma is that Chris Langan is the smartest known living man, which makes it really hard for me to shrug the CTMU off as nonsense.

You can't rely too much on intelligence tests, especially in the super-high range. The tester himself admitted that Langan fell outside the design range of the test, so the listed score was an extrapolation. Further, IQ measurements, especially at the extremes and especially on only a single test (and as far as I could tell from the wikipedia article, he was only tested once) measure test-taking ability as much as general intelligence.

Even if he is the most intelligent man alive, intelligence does not automatically mean that you reach the right answer. All evidence points to it being rubbish.