So what is the difference between moral ambition and hubris?

To me limiting oneself to “idealistic but not ambitious” with a focus on fulfilling relationships and positive impact on family, friends, and local community seems like a good way to go.

“To do evil a human being must first of all believe that what he's doing is good, or else that it's a well-considered act in conformity with natural law. Fortunately, it is in the nature of the human being to seek a justification for his actions... Ideology—that is what gives the evildoing its long-sought justification and gives the evildoer the necessary steadfastness and determination.” - Aleksandr Solzhenitsyn