From what I've read
From what I've read, and I've followed cycling for decades and the possibility of him being a cheat has always been there, Lance is giving up the fight because he doesn't want the piles of evidence that they have against him to become public.
As for the tests, the best cheaters have always been just ahead of the tests. They are using things that they do not have test for (thats why that Balco drug was called "The Clear", because there was no test for it).
And while it is not proven, there are many studies that link testicular cancer and the use of different performance enhancing drugs. If someone were to look into it (and there are a couple of articles out that that do) and a link can be found between Lance's actions and his cancer, sadly it will affect his ability to raise funds for cancer.
2011 Cross Country
Stage One Exhaust