he is the only one that can help himself. If he is this influenced by his own mother's comments and opinions still it's very unlikely that this will change. When you mentioned he had 2 divorces, well I figured ok he's not a kid but 76?! Unless you can somehow make him see the light and realize he's being controlled and doesn't need to be in that situation, he won't. The likelihood of you being able to bring that to his attention and have him act on it is very improbable.

as skeezyks said, you'll have to decide whether the dynamic is one you can deal with.