I've never posted before, so hi!
But, I've felt for a long time now that both CA and GA have been playing ICA. They know what she is like, and that she is a liar who often times didn't tell them the truth. I think going along with her stories, acting as if they supported her, was just that, an act. I would bet this was something the family often did...go along with her and let the situation work itself out. That would be enough to be a breaking point between GA and CA and have him telling people his marriage could be ending.
I know this means they would have had to have really put on an act for a really long time...but if they thought for all that time that they'd eventually convince her through their support and actions to let her guard down and give them any piece of info...it would have been worth all they've done, said, and made people believe about them. They would have done anything for Caylee, but they were willing to let Casey think they'd do anything for her.
I think George is testifying for Caylee. I don't think he's lying, beyond the omission of the fact that yes, he thought Casey did something long before he is willing to admit to.