Gaullian amour-propre = French self-love
He concluded that he would confront the problem of French conceit by learning the language.
The author is using ironic language. He is portraying Kennedy as one who makes impulsive decisions, and then does what he can to fulfill them.
To pursue with improvisation means to take disorganized and unplanned measures to meet an objective.
So yes, his approach is backwards, because he enjoyed being decisive more than thinking through the consequences of his decisions.