Is Young Earth Creationism a theory in crisis? Are Christians abandoning Young Earth Creationism in droves?

No, It's not a theory in crisis BECAUSE IT'S NOT A THEORY. Young Earth Creation is just a hypothesis - untestable and unprovable and with no evidence to support it. A theory can be tested and proved or disproved. Evolution is a theory which has a mountain of evidence to support it - so much that you can consider it fact. It's still open to someone coming along with an alternate hypothesis which could, if proven, consign it to the history books. But it hasn't happened yet despite the best efforts of countless scientists who would LOVE to be the person who proved Darwin wrong.