There are lots of theories as to why the failures occured.
James you sound like a software engineer. Use the word "theory" here and think that you have something like a scientific theory is an enormous streach. It is so enormous as to be wrong.
The speed of light in a vacuum is still constant. You have misunderstood the experiments you have been reading about.
Your comments about the moon's behaviour shows a futher misunderstanding of the mechanics involved.
see:
http://curious.astro.cornell.edu/question.php?number=124
The tidal forces on the earth (as has been discussed elsewhere ) are slowin the earth's rotation. This is putting energy into the moons revolution about the earth and causing it to spiral outward.